xfs: bounds-check buffer log item's dirty bitmap

xlog_recover_do_reg_buffer() replays each dirty region a buffer log item's bitmap describes into the in-core buffer read for that log item:

	memcpy(xfs_buf_offset(bp, (uint)bit << XFS_BLF_SHIFT),
		item->ri_buf[i].iov_base,
		nbits << XFS_BLF_SHIFT);

The only thing standing between that destination offset and the end of "bp" is:

	ASSERT(BBTOB(bp->b_length) >=
	       ((uint)bit << XFS_BLF_SHIFT) + (nbits << XFS_BLF_SHIFT));

"bp" is sized directly from the logged, attacker-controlled buf_f->blf_len (xlog_recover_buf_commit_pass2() -> xfs_buf_read(..., buf_f->blf_blkno, buf_f->blf_len, ...)), while "bit"/"nbits" come from the logged dirty bitmap (buf_f->blf_data_map), also attacker-controlled. Nothing else relates the two: the source side is trimmed against the log iovec length a few lines down (item->ri_buf[i].iov_len), but the destination side has no equivalent runtime check.

ASSERT() compiles to a no-op on production (non-DEBUG, non-XFS_WARN) kernels, which is exactly where this matters. A dirty log record whose buffer-log-format item logs a small blf_len (e.g. 1, a 512-byte buffer) together with a dirty bitmap bit that indexes past that buffer drives the memcpy() above straight past the end of the recovered buffer's backing allocation, corrupting adjacent kernel heap memory during mount-time log recovery of a crafted (or merely corrupt) XFS image. This is reachable by anyone who can get such an image mounted (CAP_SYS_ADMIN in the init namespace, or automount of removable/untrusted media) -- the standard malicious-filesystem threat model XFS's other verifiers guard against. Found with a KASAN-enabled kernel: a crafted image with a small blf_len and an out-of-range bitmap bit produces a slab-out-of-bounds write during log recovery.

Nearby recovery code already treats this class of "logged size doesn't match reality" problem as a real runtime condition rather than an invariant to assert on. In this very function, the dquot sanity check a few lines below does exactly that:

	if (item->ri_buf[i].iov_len < size_disk_dquot) {
		xfs_alert(mp, "XFS: dquot too small (%zd) in %s.", ...);
		goto next;
	}

and its sibling xlog_recover_do_inode_buffer(), a little further down in this same file, converts the equivalent destination-bounds ASSERT() into a real XFS_IS_CORRUPT() check that aborts recovery of the item instead of trusting the log:

	ASSERT((reg_buf_offset + reg_buf_bytes) <= BBTOB(bp->b_length));
	...
	if (XFS_IS_CORRUPT(mp, *logged_nextp == 0)) {
		xfs_alert(mp, "Bad inode buffer log record ...");
		return -EFSCORRUPTED;
	}

Give xlog_recover_do_reg_buffer() the same treatment: turn the destination-bounds ASSERT() into a real XFS_IS_CORRUPT() check, log it with xfs_alert() (matching xlog_recover_do_inode_buffer() and the xfs_dquot_item_recover.c size checks), and fail recovery of this buffer with -EFSCORRUPTED instead of copying past its end. Since the function now needs to report failure, change it from "STATIC void" to "STATIC int" and propagate the new error out of all three callers:

- xlog_recover_do_primary_sb_buffer(), which already returns int

    and already checks other error conditions inline;

- xlog_recover_do_dquot_buffer(), which returns a "dirty" bool to its one caller; it gains an "int *error" out-parameter so the caller can distinguish "buffer intentionally skipped" from "buffer recovery failed";
- the plain regular-buffer branch of xlog_recover_buf_commit_pass2(), which already has an in-scope "error" local used by the sibling branches right next to it.

This is a minimal, targeted fix: it does not change any successful recovery path (the new check only rejects logs that were already violating the invariant the ASSERT() was documenting), and it mirrors the exact validate-and-fail idiom already used a few lines away in the same file and in fs/xfs/xfs_dquot_item_recover.c.

Verified on a v6.19 KASAN-enabled kernel (CONFIG_XFS_DEBUG=n): mount of a crafted image whose buffer log item's dirty bitmap indexes past its logged blf_len trips a KASAN slab-out-of-bounds write in xlog_recover_do_reg_buffer() before this patch; with the patch applied, mounting the same image fails recovery with -EFSCORRUPTED and no KASAN report is produced.

Cc [email protected]

Signed-off-by Ibrahim Hashimov <[email protected]>

Assisted-by AuditCode-AI:2026.07

---
v2: no functional change; v1 was sent with an empty Subject line due to
a local git send-email glitch (leading blank line in the patch file).

 fs/xfs/xfs_buf_item_recover.c | 48 ++++++++++++++++++++++++++++-------
 1 file changed, 39 insertions(+), 9 deletions(-)

fs/xfs/xfs_buf_item_recover.c +1 -3

index 02b95b89d1b5..521e5f544caf 100644
@@ -461,7 +461,7 @@ xlog_recover_validate_buf_type(
  * given buffer.  The bitmap in the buf log format structure indicates
  * where to place the logged data.
  */
-STATIC void
+STATIC int
 xlog_recover_do_reg_buffer(
 	struct xfs_mount		*mp,
 	struct xlog_recover_item	*item,

@@ -489,8 +489,25 @@ xlog_recover_do_reg_buffer(
 		ASSERT(nbits > 0);
 		ASSERT(item->ri_buf[i].iov_base != NULL);
 		ASSERT(item->ri_buf[i].iov_len % XFS_BLF_CHUNK == 0);
-		ASSERT(BBTOB(bp->b_length) >=
-		       ((uint)bit << XFS_BLF_SHIFT) + (nbits << XFS_BLF_SHIFT));

fs/xfs/xfs_buf_item_recover.c +13 -1

+		if (XFS_IS_CORRUPT(mp, BBTOB(bp->b_length) <
+				((uint)bit << XFS_BLF_SHIFT) +
+				(nbits << XFS_BLF_SHIFT))) {
+			xfs_alert(mp,
+	"Bad buffer log item dirty bitmap (bit %d, nbits %d) for %d-byte buffer at daddr 0x%llx.",
+				bit, nbits, BBTOB(bp->b_length),
+				xfs_buf_daddr(bp));
+			return -EFSCORRUPTED;
+		}
 
 		/*
 		 * The dirty regions logged in the buffer, even though

@@ -544,6 +561,7 @@ xlog_recover_do_reg_buffer(
 	ASSERT(i == item->ri_total);
 
 	xlog_recover_validate_buf_type(mp, bp, buf_f, current_lsn);
+	return 0;
 }
 
 /*

@@ -553,7 +571,9 @@ xlog_recover_do_reg_buffer(
  * Else, treat it as a regular buffer and do recovery.
  *
  * Return false if the buffer was tossed and true if we recovered the buffer to
- * indicate to the caller if the buffer needs writing.
+ * indicate to the caller if the buffer needs writing.  *error is set if
+ * recovery of the buffer failed and the caller must abort replay of this
+ * buffer.
  */
 STATIC bool
 xlog_recover_do_dquot_buffer(

fs/xfs/xfs_buf_item_recover.c +5 -2

 {
 	uint			type;
 
+	*error = 0;
 	trace_xfs_log_recover_buf_dquot_buf(log, buf_f);
 
 	/*

@@ -586,7 +608,7 @@ xlog_recover_do_dquot_buffer(
 	if (log->l_quotaoffs_flag & type)
 		return false;
 
-	xlog_recover_do_reg_buffer(mp, item, bp, buf_f, NULLCOMMITLSN);
+	*error = xlog_recover_do_reg_buffer(mp, item, bp, buf_f, NULLCOMMITLSN);
 	return true;
 }
 

@@ -724,7 +746,9 @@ xlog_recover_do_primary_sb_buffer(
 	xfs_rgnumber_t			orig_rgcount = mp->m_sb.sb_rgcount;
 	int				error;
 
-	xlog_recover_do_reg_buffer(mp, item, bp, buf_f, current_lsn);
+	error = xlog_recover_do_reg_buffer(mp, item, bp, buf_f, current_lsn);
+	if (error)
+		return error;
 
 	if (orig_agcount == 0) {
 		xfs_alert(mp, "Trying to grow file system without AGs");

fs/xfs/xfs_buf_item_recover.c +4 -1

 	} else if ((xfs_blft_from_flags(buf_f) & XFS_BLFT_SB_BUF) &&

@@ -1105,7 +1132,10 @@ xlog_recover_buf_commit_pass2(
 			xfs_buf_relse(rtsb_bp);
 		}
 	} else {
-		xlog_recover_do_reg_buffer(mp, item, bp, buf_f, current_lsn);
+		error = xlog_recover_do_reg_buffer(mp, item, bp, buf_f,
+						   current_lsn);
+		if (error)
+			goto out_release;
 	}
 
 	/*

Signature · 1 line

2.50.1 (Apple Git-155)

xlog_recover_do_reg_buffer() replays each dirty region described by a buffer log item's bitmap into the buffer read for that item:

	memcpy(xfs_buf_offset(bp, (uint)bit << XFS_BLF_SHIFT),
		item->ri_buf[i].iov_base,
		nbits << XFS_BLF_SHIFT);

The destination offset (bit/nbits, from the logged dirty bitmap) and the buffer size (from the logged blf_len) are both attacker-controlled and otherwise unrelated, yet the only thing bounding the copy is an ASSERT(), which compiles away on production kernels. A crafted image logging a small blf_len together with a bitmap bit past the end of that buffer drives the memcpy() past the buffer's allocation, corrupting adjacent kernel heap during mount-time log recovery. This is reachable by anyone who can get a crafted image mounted -- the malicious-filesystem threat model XFS already guards against elsewhere.

Turn the ASSERT() into a real XFS_IS_CORRUPT() check that aborts recovery of the buffer with -EFSCORRUPTED, consistent with the validate-and-fail idiom already used in xlog_recover_do_inode_buffer() and xfs_dquot_item_recover.c. xlog_recover_do_reg_buffer() therefore becomes STATIC int and its three callers propagate the error.

Found and confirmed with KASAN on a CONFIG_XFS_DEBUG=n build: the crafted image trips a slab-out-of-bounds write before this change and fails recovery cleanly with -EFSCORRUPTED after it.

Fixes 1da177e4c3f4 ("Linux-2.6.12-rc2")

Cc [email protected]

Signed-off-by Ibrahim Hashimov <[email protected]>

Assisted-by AuditCode-AI:2026.07

---
v3: trim the changelog per Brian Foster's review; no code change. Add a
Fixes: tag -- the destination-bounds check has been an ASSERT since the initial git import (2.6.12-rc2), so it predates the git era.
v2: resend; v1 went out with an empty Subject line due to a local
git send-email glitch (leading blank line in the patch file).

 fs/xfs/xfs_buf_item_recover.c | 48 ++++++++++++++++++++++++++++-------
 1 file changed, 39 insertions(+), 9 deletions(-)

fs/xfs/xfs_buf_item_recover.c +21 -3

index 02b95b89d1b5..521e5f544caf 100644
@@ -461,7 +461,7 @@ xlog_recover_validate_buf_type(
  * given buffer.  The bitmap in the buf log format structure indicates
  * where to place the logged data.
  */
-STATIC void
+STATIC int
 xlog_recover_do_reg_buffer(
 	struct xfs_mount		*mp,
 	struct xlog_recover_item	*item,

@@ -489,8 +489,25 @@ xlog_recover_do_reg_buffer(
 		ASSERT(nbits > 0);
 		ASSERT(item->ri_buf[i].iov_base != NULL);
 		ASSERT(item->ri_buf[i].iov_len % XFS_BLF_CHUNK == 0);
-		ASSERT(BBTOB(bp->b_length) >=
-		       ((uint)bit << XFS_BLF_SHIFT) + (nbits << XFS_BLF_SHIFT));
+
+		/*
+		 * The bitmap is only trustworthy to the extent that it
+		 * describes a region that actually fits inside the buffer we
+		 * read in based on the (attacker-controlled) blf_len.  Do not
+		 * rely on an ASSERT() for this -- it compiles away entirely
+		 * on non-DEBUG kernels, which is exactly where this matters,
+		 * so validate it for real and abort recovery of this buffer
+		 * rather than copying past the end of it.
+		 */
+		if (XFS_IS_CORRUPT(mp, BBTOB(bp->b_length) <
+				((uint)bit << XFS_BLF_SHIFT) +
+				(nbits << XFS_BLF_SHIFT))) {
+			xfs_alert(mp,
+	"Bad buffer log item dirty bitmap (bit %d, nbits %d) for %d-byte buffer at daddr 0x%llx.",
+				bit, nbits, BBTOB(bp->b_length),
+				xfs_buf_daddr(bp));
+			return -EFSCORRUPTED;
+		}
 
 		/*
 		 * The dirty regions logged in the buffer, even though

@@ -544,6 +561,7 @@ xlog_recover_do_reg_buffer(
 	ASSERT(i == item->ri_total);
 
 	xlog_recover_validate_buf_type(mp, bp, buf_f, current_lsn);
+	return 0;
 }
 
 /*

fs/xfs/xfs_buf_item_recover.c +15 -5

  */
 STATIC bool
 xlog_recover_do_dquot_buffer(

@@ -561,10 +581,12 @@ xlog_recover_do_dquot_buffer(
 	struct xlog			*log,
 	struct xlog_recover_item	*item,
 	struct xfs_buf			*bp,
-	struct xfs_buf_log_format	*buf_f)
+	struct xfs_buf_log_format	*buf_f,
+	int				*error)
 {
 	uint			type;
 
+	*error = 0;
 	trace_xfs_log_recover_buf_dquot_buf(log, buf_f);
 
 	/*

@@ -586,7 +608,7 @@ xlog_recover_do_dquot_buffer(
 	if (log->l_quotaoffs_flag & type)
 		return false;
 
-	xlog_recover_do_reg_buffer(mp, item, bp, buf_f, NULLCOMMITLSN);
+	*error = xlog_recover_do_reg_buffer(mp, item, bp, buf_f, NULLCOMMITLSN);
 	return true;
 }
 

@@ -724,7 +746,9 @@ xlog_recover_do_primary_sb_buffer(
 	xfs_rgnumber_t			orig_rgcount = mp->m_sb.sb_rgcount;
 	int				error;
 
-	xlog_recover_do_reg_buffer(mp, item, bp, buf_f, current_lsn);
+	error = xlog_recover_do_reg_buffer(mp, item, bp, buf_f, current_lsn);
+	if (error)
+		return error;
 
 	if (orig_agcount == 0) {
 		xfs_alert(mp, "Trying to grow file system without AGs");

@@ -1083,7 +1107,10 @@ xlog_recover_buf_commit_pass2(
 		  (XFS_BLF_UDQUOT_BUF|XFS_BLF_PDQUOT_BUF|XFS_BLF_GDQUOT_BUF)) {
 		bool	dirty;
 
-		dirty = xlog_recover_do_dquot_buffer(mp, log, item, bp, buf_f);
+		dirty = xlog_recover_do_dquot_buffer(mp, log, item, bp, buf_f,
+						     &error);
+		if (error)
+			goto out_release;
 		if (!dirty)
 			goto out_release;
 	} else if ((xfs_blft_from_flags(buf_f) & XFS_BLFT_SB_BUF) &&

@@ -1105,7 +1132,10 @@ xlog_recover_buf_commit_pass2(
 			xfs_buf_relse(rtsb_bp);
 		}
 	} else {
-		xlog_recover_do_reg_buffer(mp, item, bp, buf_f, current_lsn);
+		error = xlog_recover_do_reg_buffer(mp, item, bp, buf_f,
+						   current_lsn);
+		if (error)
+			goto out_release;
 	}
 
 	/*

Signature · 1 line

2.50.1 (Apple Git-155)

xlog_recover_do_reg_buffer() replays each dirty region described by a buffer log item's bitmap into the buffer read for that item:

	memcpy(xfs_buf_offset(bp, (uint)bit << XFS_BLF_SHIFT),
		item->ri_buf[i].iov_base,
		nbits << XFS_BLF_SHIFT);

The destination offset (bit/nbits, from the logged dirty bitmap) and the buffer size (from the logged blf_len) are both attacker-controlled and otherwise unrelated, yet the only thing bounding the copy is an ASSERT(), which compiles away on production kernels. A crafted image logging a small blf_len together with a bitmap bit past the end of that buffer drives the memcpy() past the buffer's allocation, corrupting adjacent kernel heap during mount-time log recovery. This is reachable by anyone who can get a crafted image mounted -- the malicious-filesystem threat model XFS already guards against elsewhere.

Turn the ASSERT() into a real XFS_IS_CORRUPT() check that aborts recovery of the buffer with -EFSCORRUPTED, consistent with the validate-and-fail idiom already used in xlog_recover_do_inode_buffer() and xfs_dquot_item_recover.c. xlog_recover_do_reg_buffer() therefore becomes STATIC int and its three callers propagate the error.

Found and confirmed with KASAN on a CONFIG_XFS_DEBUG=n build: the crafted image trips a slab-out-of-bounds write before this change and fails recovery cleanly with -EFSCORRUPTED after it.

Fixes 1da177e4c3f4 ("Linux-2.6.12-rc2")

Cc [email protected]

Signed-off-by Ibrahim Hashimov <[email protected]>

Assisted-by AuditCode-AI:2026.07

---
v4: fold xlog_recover_do_dquot_buffer()'s bool return and error
out-parameter into a single int return (1 if dirty, 0 if clean, or a negative errno on failure), per Darrick's review. No behavioural change.
v3: trim the changelog per Brian Foster's review. Add a Fixes: tag --
the destination-bounds check has been an ASSERT since the initial git import (2.6.12-rc2), so it predates the git era.
v2: resend; v1 went out with an empty Subject line due to a local
git send-email glitch (leading blank line in the patch file).

 fs/xfs/xfs_buf_item_recover.c | 56 ++++++++++++++++++++++++++++-------------
 1 file changed, 40 insertions(+), 16 deletions(-)

fs/xfs/xfs_buf_item_recover.c +40 -16

index 02b95b89d1b5..cf2b07ebc6f3 100644
@@ -461,7 +461,7 @@ xlog_recover_validate_buf_type(
  * given buffer.  The bitmap in the buf log format structure indicates
  * where to place the logged data.
  */
-STATIC void
+STATIC int
 xlog_recover_do_reg_buffer(
 	struct xfs_mount		*mp,
 	struct xlog_recover_item	*item,

@@ -489,8 +489,24 @@ xlog_recover_do_reg_buffer(
 		ASSERT(nbits > 0);
 		ASSERT(item->ri_buf[i].iov_base != NULL);
 		ASSERT(item->ri_buf[i].iov_len % XFS_BLF_CHUNK == 0);
-		ASSERT(BBTOB(bp->b_length) >=
-		       ((uint)bit << XFS_BLF_SHIFT) + (nbits << XFS_BLF_SHIFT));
+		/*
+		 * The bitmap is only trustworthy to the extent that it
+		 * describes a region that actually fits inside the buffer we
+		 * read in based on the (attacker-controlled) blf_len.  Do not
+		 * rely on an ASSERT() for this -- it compiles away entirely on
+		 * non-DEBUG kernels, which is exactly where this matters, so
+		 * validate it for real and abort recovery of this buffer rather
+		 * than copying past the end of it.
+		 */
+		if (XFS_IS_CORRUPT(mp, BBTOB(bp->b_length) <
+				((uint)bit << XFS_BLF_SHIFT) +
+				(nbits << XFS_BLF_SHIFT))) {
+			xfs_alert(mp,
+	"Bad buffer log item dirty bitmap (bit %d, nbits %d) for %d-byte buffer at daddr 0x%llx.",
+				bit, nbits, BBTOB(bp->b_length),
+				xfs_buf_daddr(bp));
+			return -EFSCORRUPTED;
+		}
 
 		/*
 		 * The dirty regions logged in the buffer, even though

@@ -544,6 +560,7 @@ xlog_recover_do_reg_buffer(
 	ASSERT(i == item->ri_total);
 
 	xlog_recover_validate_buf_type(mp, bp, buf_f, current_lsn);
+	return 0;
 }
 
 /*

@@ -552,10 +569,10 @@ xlog_recover_do_reg_buffer(
  * (ie. USR or GRP), then just toss this buffer away; don't recover it.
  * Else, treat it as a regular buffer and do recovery.
  *
- * Return false if the buffer was tossed and true if we recovered the buffer to
- * indicate to the caller if the buffer needs writing.
+ * Return 0 if the buffer was not recovered (tossed), 1 if it was recovered and
+ * needs writing, or a negative errno if recovery of the buffer failed.
  */
-STATIC bool
+STATIC int
 xlog_recover_do_dquot_buffer(
 	struct xfs_mount		*mp,
 	struct xlog			*log,

@@ -564,6 +581,7 @@ xlog_recover_do_dquot_buffer(
 	struct xfs_buf_log_format	*buf_f)
 {
 	uint			type;
+	int			error;
 
 	trace_xfs_log_recover_buf_dquot_buf(log, buf_f);
 

@@ -571,7 +589,7 @@ xlog_recover_do_dquot_buffer(
 	 * Filesystems are required to send in quota flags at mount time.
 	 */
 	if (!mp->m_qflags)
-		return false;
+		return 0;
 
 	type = 0;
 	if (buf_f->blf_flags & XFS_BLF_UDQUOT_BUF)

@@ -584,10 +602,12 @@ xlog_recover_do_dquot_buffer(
 	 * This type of quotas was turned off, so ignore this buffer
 	 */
 	if (log->l_quotaoffs_flag & type)
-		return false;
+		return 0;
 
-	xlog_recover_do_reg_buffer(mp, item, bp, buf_f, NULLCOMMITLSN);
-	return true;
+	error = xlog_recover_do_reg_buffer(mp, item, bp, buf_f, NULLCOMMITLSN);
+	if (error)
+		return error;
+	return 1;
 }
 
 /*

@@ -724,7 +744,9 @@ xlog_recover_do_primary_sb_buffer(
 	xfs_rgnumber_t			orig_rgcount = mp->m_sb.sb_rgcount;
 	int				error;
 
-	xlog_recover_do_reg_buffer(mp, item, bp, buf_f, current_lsn);
+	error = xlog_recover_do_reg_buffer(mp, item, bp, buf_f, current_lsn);
+	if (error)
+		return error;
 
 	if (orig_agcount == 0) {
 		xfs_alert(mp, "Trying to grow file system without AGs");

@@ -1081,11 +1103,10 @@ xlog_recover_buf_commit_pass2(
 			goto out_release;
 	} else if (buf_f->blf_flags &
 		  (XFS_BLF_UDQUOT_BUF|XFS_BLF_PDQUOT_BUF|XFS_BLF_GDQUOT_BUF)) {
-		bool	dirty;
-
-		dirty = xlog_recover_do_dquot_buffer(mp, log, item, bp, buf_f);
-		if (!dirty)
+		error = xlog_recover_do_dquot_buffer(mp, log, item, bp, buf_f);
+		if (error <= 0)
 			goto out_release;
+		error = 0;
 	} else if ((xfs_blft_from_flags(buf_f) & XFS_BLFT_SB_BUF) &&
 			xfs_buf_daddr(bp) == 0) {
 		error = xlog_recover_do_primary_sb_buffer(mp, item, bp, buf_f,

@@ -1105,7 +1126,10 @@ xlog_recover_buf_commit_pass2(
 			xfs_buf_relse(rtsb_bp);
 		}
 	} else {
-		xlog_recover_do_reg_buffer(mp, item, bp, buf_f, current_lsn);
+		error = xlog_recover_do_reg_buffer(mp, item, bp, buf_f,
+						   current_lsn);
+		if (error)
+			goto out_release;
 	}
 
 	/*

Signature · 1 line

2.50.1 (Apple Git-155)

Quoted 23 lines · Ibrahim Hashimov

xlog_recover_do_reg_buffer() replays each dirty region described by a buffer log item's bitmap into the buffer read for that item:

	memcpy(xfs_buf_offset(bp, (uint)bit << XFS_BLF_SHIFT),
		item->ri_buf[i].iov_base,
		nbits << XFS_BLF_SHIFT);

The destination offset (bit/nbits, from the logged dirty bitmap) and the buffer size (from the logged blf_len) are both attacker-controlled and otherwise unrelated, yet the only thing bounding the copy is an ASSERT(), which compiles away on production kernels. A crafted image logging a small blf_len together with a bitmap bit past the end of that buffer drives the memcpy() past the buffer's allocation, corrupting adjacent kernel heap during mount-time log recovery. This is reachable by anyone who can get a crafted image mounted -- the malicious-filesystem threat model XFS already guards against elsewhere.

Turn the ASSERT() into a real XFS_IS_CORRUPT() check that aborts recovery of the buffer with -EFSCORRUPTED, consistent with the validate-and-fail idiom already used in xlog_recover_do_inode_buffer() and xfs_dquot_item_recover.c. xlog_recover_do_reg_buffer() therefore becomes STATIC int and its three callers propagate the error.

Quoted 8 lines

Found and confirmed with KASAN on a CONFIG_XFS_DEBUG=n build: the crafted image trips a slab-out-of-bounds write before this change and fails recovery cleanly with -EFSCORRUPTED after it.

Fixes 1da177e4c3f4 ("Linux-2.6.12-rc2")

Cc [email protected]

Signed-off-by Ibrahim Hashimov <[email protected]>

Assisted-by AuditCode-AI:2026.07

Looks fine to me now, thanks for making those edits.

Reviewed-by "Darrick J. Wong" <[email protected]>

--D

Quoted 18 lines

---
v4: fold xlog_recover_do_dquot_buffer()'s bool return and error
out-parameter into a single int return (1 if dirty, 0 if clean, or a negative errno on failure), per Darrick's review. No behavioural change.
v3: trim the changelog per Brian Foster's review. Add a Fixes: tag --
the destination-bounds check has been an ASSERT since the initial git import (2.6.12-rc2), so it predates the git era.
v2: resend; v1 went out with an empty Subject line due to a local
git send-email glitch (leading blank line in the patch file).

 fs/xfs/xfs_buf_item_recover.c | 56 ++++++++++++++++++++++++++++-------------
 1 file changed, 40 insertions(+), 16 deletions(-)

fs/xfs/xfs_buf_item_recover.c +0 -0

index 02b95b89d1b5..cf2b07ebc6f3 100644

fs/xfs/xfs_buf_item_recover.c xlog_recover_buf_commit_pass2( · line 1108

Quoted 11 lines

fs/xfs/xfs_buf_item_recover.c +2 -4

@@ -1081,11 +1103,10 @@ xlog_recover_buf_commit_pass2(
 			goto out_release;
 	} else if (buf_f->blf_flags &
 		  (XFS_BLF_UDQUOT_BUF|XFS_BLF_PDQUOT_BUF|XFS_BLF_GDQUOT_BUF)) {
-		bool	dirty;
-
-		dirty = xlog_recover_do_dquot_buffer(mp, log, item, bp, buf_f);
-		if (!dirty)
+		error = xlog_recover_do_dquot_buffer(mp, log, item, bp, buf_f);
+		if (error <= 0)
 			goto out_release;

Quoted 18 lines

fs/xfs/xfs_buf_item_recover.c +5 -1

+		error = 0;
 	} else if ((xfs_blft_from_flags(buf_f) & XFS_BLFT_SB_BUF) &&
 			xfs_buf_daddr(bp) == 0) {
 		error = xlog_recover_do_primary_sb_buffer(mp, item, bp, buf_f,

@@ -1105,7 +1126,10 @@ xlog_recover_buf_commit_pass2(
 			xfs_buf_relse(rtsb_bp);
 		}
 	} else {
-		xlog_recover_do_reg_buffer(mp, item, bp, buf_f, current_lsn);
+		error = xlog_recover_do_reg_buffer(mp, item, bp, buf_f,
+						   current_lsn);
+		if (error)
+			goto out_release;
 	}
 
 	/*

Signature · 1 line

2.50.1 (Apple Git-155)

Quoted 56 lines · Darrick J. Wong

Quoted 23 lines · Ibrahim Hashimov

xlog_recover_do_reg_buffer() replays each dirty region described by a buffer log item's bitmap into the buffer read for that item:

	memcpy(xfs_buf_offset(bp, (uint)bit << XFS_BLF_SHIFT),
		item->ri_buf[i].iov_base,
		nbits << XFS_BLF_SHIFT);

The destination offset (bit/nbits, from the logged dirty bitmap) and the buffer size (from the logged blf_len) are both attacker-controlled and otherwise unrelated, yet the only thing bounding the copy is an ASSERT(), which compiles away on production kernels. A crafted image logging a small blf_len together with a bitmap bit past the end of that buffer drives the memcpy() past the buffer's allocation, corrupting adjacent kernel heap during mount-time log recovery. This is reachable by anyone who can get a crafted image mounted -- the malicious-filesystem threat model XFS already guards against elsewhere.

Turn the ASSERT() into a real XFS_IS_CORRUPT() check that aborts recovery of the buffer with -EFSCORRUPTED, consistent with the validate-and-fail idiom already used in xlog_recover_do_inode_buffer() and xfs_dquot_item_recover.c. xlog_recover_do_reg_buffer() therefore becomes STATIC int and its three callers propagate the error.

Quoted 8 lines

Found and confirmed with KASAN on a CONFIG_XFS_DEBUG=n build: the crafted image trips a slab-out-of-bounds write before this change and fails recovery cleanly with -EFSCORRUPTED after it.

Fixes 1da177e4c3f4 ("Linux-2.6.12-rc2")

Cc [email protected]

Signed-off-by Ibrahim Hashimov <[email protected]>

Assisted-by AuditCode-AI:2026.07

Looks fine to me now, thanks for making those edits.

Reviewed-by "Darrick J. Wong" <[email protected]>

--D

Quoted 18 lines

---
v4: fold xlog_recover_do_dquot_buffer()'s bool return and error
out-parameter into a single int return (1 if dirty, 0 if clean, or a negative errno on failure), per Darrick's review. No behavioural change.
v3: trim the changelog per Brian Foster's review. Add a Fixes: tag --
the destination-bounds check has been an ASSERT since the initial git import (2.6.12-rc2), so it predates the git era.
v2: resend; v1 went out with an empty Subject line due to a local
git send-email glitch (leading blank line in the patch file).

 fs/xfs/xfs_buf_item_recover.c | 56 ++++++++++++++++++++++++++++-------------
 1 file changed, 40 insertions(+), 16 deletions(-)

fs/xfs/xfs_buf_item_recover.c +0 -0

index 02b95b89d1b5..cf2b07ebc6f3 100644

...

Quoted 11 lines

fs/xfs/xfs_buf_item_recover.c xlog_recover_buf_commit_pass2( · line 1108

Quoted 11 lines

fs/xfs/xfs_buf_item_recover.c +2 -4

@@ -1081,11 +1103,10 @@ xlog_recover_buf_commit_pass2(
 			goto out_release;
 	} else if (buf_f->blf_flags &
 		  (XFS_BLF_UDQUOT_BUF|XFS_BLF_PDQUOT_BUF|XFS_BLF_GDQUOT_BUF)) {
-		bool	dirty;
-
-		dirty = xlog_recover_do_dquot_buffer(mp, log, item, bp, buf_f);
-		if (!dirty)
+		error = xlog_recover_do_dquot_buffer(mp, log, item, bp, buf_f);
+		if (error <= 0)
 			goto out_release;

I might suggest something like:

		/* reset error since > 0 means to write the buffer */

... or maybe we can phrase that better. But regardless LGTM now as well, thanks:

Reviewed-by Brian Foster <[email protected]>

Quoted 19 lines

Quoted 18 lines

fs/xfs/xfs_buf_item_recover.c +5 -1

+		error = 0;
 	} else if ((xfs_blft_from_flags(buf_f) & XFS_BLFT_SB_BUF) &&
 			xfs_buf_daddr(bp) == 0) {
 		error = xlog_recover_do_primary_sb_buffer(mp, item, bp, buf_f,

@@ -1105,7 +1126,10 @@ xlog_recover_buf_commit_pass2(
 			xfs_buf_relse(rtsb_bp);
 		}
 	} else {
-		xlog_recover_do_reg_buffer(mp, item, bp, buf_f, current_lsn);
+		error = xlog_recover_do_reg_buffer(mp, item, bp, buf_f,
+						   current_lsn);
+		if (error)
+			goto out_release;
 	}
 
 	/*

Signature · 1 line

2.50.1 (Apple Git-155)

xlog_recover_do_reg_buffer() replays each dirty region described by a buffer log item's bitmap into the buffer read for that item:

	memcpy(xfs_buf_offset(bp, (uint)bit << XFS_BLF_SHIFT),
		item->ri_buf[i].iov_base,
		nbits << XFS_BLF_SHIFT);

The destination offset (bit/nbits, from the logged dirty bitmap) and the buffer size (from the logged blf_len) are both attacker-controlled and otherwise unrelated, yet the only thing bounding the copy is an ASSERT(), which compiles away on production kernels. A crafted image logging a small blf_len together with a bitmap bit past the end of that buffer drives the memcpy() past the buffer's allocation, corrupting adjacent kernel heap during mount-time log recovery. This is reachable by anyone who can get a crafted image mounted -- the malicious-filesystem threat model XFS already guards against elsewhere.

Turn the ASSERT() into a real XFS_IS_CORRUPT() check that aborts recovery of the buffer with -EFSCORRUPTED, consistent with the validate-and-fail idiom already used in xlog_recover_do_inode_buffer() and xfs_dquot_item_recover.c. xlog_recover_do_reg_buffer() therefore becomes STATIC int and its three callers propagate the error.

Found and confirmed with KASAN on a CONFIG_XFS_DEBUG=n build: the crafted image trips a slab-out-of-bounds write before this change and fails recovery cleanly with -EFSCORRUPTED after it.

Fixes 1da177e4c3f4 ("Linux-2.6.12-rc2")

Cc [email protected]

Signed-off-by Ibrahim Hashimov <[email protected]>

Assisted-by AuditCode-AI:2026.07

Reviewed-by "Darrick J. Wong" <[email protected]>

Reviewed-by Brian Foster <[email protected]>

---
v5: add the "/* write dirty buffer */" comment Darrick and Brian asked
for above the error reset; no functional change. Carry their Reviewed-by tags.
v4: fold xlog_recover_do_dquot_buffer()'s bool return and error
out-parameter into a single int return (1 if dirty, 0 if clean, or a negative errno on failure), per Darrick's review.
v3: trim the changelog per Brian Foster's review. Add a Fixes: tag --
the destination-bounds check has been an ASSERT since the initial git import (2.6.12-rc2), so it predates the git era.
v2: resend; v1 went out with an empty Subject line due to a local
git send-email glitch (leading blank line in the patch file).

 fs/xfs/xfs_buf_item_recover.c | 57 +++++++++++++++++++++++++++++--------------
 1 file changed, 41 insertions(+), 16 deletions(-)

fs/xfs/xfs_buf_item_recover.c +41 -16

index 02b95b89d1b5..240deb3f7827 100644
@@ -461,7 +461,7 @@ xlog_recover_validate_buf_type(
  * given buffer.  The bitmap in the buf log format structure indicates
  * where to place the logged data.
  */
-STATIC void
+STATIC int
 xlog_recover_do_reg_buffer(
 	struct xfs_mount		*mp,
 	struct xlog_recover_item	*item,

@@ -489,8 +489,24 @@ xlog_recover_do_reg_buffer(
 		ASSERT(nbits > 0);
 		ASSERT(item->ri_buf[i].iov_base != NULL);
 		ASSERT(item->ri_buf[i].iov_len % XFS_BLF_CHUNK == 0);
-		ASSERT(BBTOB(bp->b_length) >=
-		       ((uint)bit << XFS_BLF_SHIFT) + (nbits << XFS_BLF_SHIFT));
+		/*
+		 * The bitmap is only trustworthy to the extent that it
+		 * describes a region that actually fits inside the buffer we
+		 * read in based on the (attacker-controlled) blf_len.  Do not
+		 * rely on an ASSERT() for this -- it compiles away entirely on
+		 * non-DEBUG kernels, which is exactly where this matters, so
+		 * validate it for real and abort recovery of this buffer rather
+		 * than copying past the end of it.
+		 */
+		if (XFS_IS_CORRUPT(mp, BBTOB(bp->b_length) <
+				((uint)bit << XFS_BLF_SHIFT) +
+				(nbits << XFS_BLF_SHIFT))) {
+			xfs_alert(mp,
+	"Bad buffer log item dirty bitmap (bit %d, nbits %d) for %d-byte buffer at daddr 0x%llx.",
+				bit, nbits, BBTOB(bp->b_length),
+				xfs_buf_daddr(bp));
+			return -EFSCORRUPTED;
+		}
 
 		/*
 		 * The dirty regions logged in the buffer, even though

@@ -544,6 +560,7 @@ xlog_recover_do_reg_buffer(
 	ASSERT(i == item->ri_total);
 
 	xlog_recover_validate_buf_type(mp, bp, buf_f, current_lsn);
+	return 0;
 }
 
 /*

@@ -552,10 +569,10 @@ xlog_recover_do_reg_buffer(
  * (ie. USR or GRP), then just toss this buffer away; don't recover it.
  * Else, treat it as a regular buffer and do recovery.
  *
- * Return false if the buffer was tossed and true if we recovered the buffer to
- * indicate to the caller if the buffer needs writing.
+ * Return 0 if the buffer was not recovered (tossed), 1 if it was recovered and
+ * needs writing, or a negative errno if recovery of the buffer failed.
  */
-STATIC bool
+STATIC int
 xlog_recover_do_dquot_buffer(
 	struct xfs_mount		*mp,
 	struct xlog			*log,

@@ -564,6 +581,7 @@ xlog_recover_do_dquot_buffer(
 	struct xfs_buf_log_format	*buf_f)
 {
 	uint			type;
+	int			error;
 
 	trace_xfs_log_recover_buf_dquot_buf(log, buf_f);
 

@@ -571,7 +589,7 @@ xlog_recover_do_dquot_buffer(
 	 * Filesystems are required to send in quota flags at mount time.
 	 */
 	if (!mp->m_qflags)
-		return false;
+		return 0;
 
 	type = 0;
 	if (buf_f->blf_flags & XFS_BLF_UDQUOT_BUF)

@@ -584,10 +602,12 @@ xlog_recover_do_dquot_buffer(
 	 * This type of quotas was turned off, so ignore this buffer
 	 */
 	if (log->l_quotaoffs_flag & type)
-		return false;
+		return 0;
 
-	xlog_recover_do_reg_buffer(mp, item, bp, buf_f, NULLCOMMITLSN);
-	return true;
+	error = xlog_recover_do_reg_buffer(mp, item, bp, buf_f, NULLCOMMITLSN);
+	if (error)
+		return error;
+	return 1;
 }
 
 /*

@@ -724,7 +744,9 @@ xlog_recover_do_primary_sb_buffer(
 	xfs_rgnumber_t			orig_rgcount = mp->m_sb.sb_rgcount;
 	int				error;
 
-	xlog_recover_do_reg_buffer(mp, item, bp, buf_f, current_lsn);
+	error = xlog_recover_do_reg_buffer(mp, item, bp, buf_f, current_lsn);
+	if (error)
+		return error;
 
 	if (orig_agcount == 0) {
 		xfs_alert(mp, "Trying to grow file system without AGs");

@@ -1081,11 +1103,11 @@ xlog_recover_buf_commit_pass2(
 			goto out_release;
 	} else if (buf_f->blf_flags &
 		  (XFS_BLF_UDQUOT_BUF|XFS_BLF_PDQUOT_BUF|XFS_BLF_GDQUOT_BUF)) {
-		bool	dirty;
-
-		dirty = xlog_recover_do_dquot_buffer(mp, log, item, bp, buf_f);
-		if (!dirty)
+		error = xlog_recover_do_dquot_buffer(mp, log, item, bp, buf_f);
+		if (error <= 0)
 			goto out_release;
+		/* write dirty buffer */
+		error = 0;
 	} else if ((xfs_blft_from_flags(buf_f) & XFS_BLFT_SB_BUF) &&
 			xfs_buf_daddr(bp) == 0) {
 		error = xlog_recover_do_primary_sb_buffer(mp, item, bp, buf_f,

@@ -1105,7 +1127,10 @@ xlog_recover_buf_commit_pass2(
 			xfs_buf_relse(rtsb_bp);
 		}
 	} else {
-		xlog_recover_do_reg_buffer(mp, item, bp, buf_f, current_lsn);
+		error = xlog_recover_do_reg_buffer(mp, item, bp, buf_f,
+						   current_lsn);
+		if (error)
+			goto out_release;
 	}
 
 	/*

Signature · 1 line

2.50.1 (Apple Git-155)

We are starting to get rid of Assisted-by tags mentioning specific models or completely getting rid of them at all.
If you are ok with it I'll just remove this tag during commit time, or if you prefer, please send a new version without the tag.

xlog_recover_do_reg_buffer() replays each dirty region described by a buffer log item's bitmap into the buffer read for that item:

	memcpy(xfs_buf_offset(bp, (uint)bit << XFS_BLF_SHIFT),
		item->ri_buf[i].iov_base,
		nbits << XFS_BLF_SHIFT);

[...]