FAILED: patch "[PATCH] erofs: fix the out-of-bounds nameoff handling for trailing" failed to apply to 5.15-stable tree

PATCH In review [email protected] 3 participants 3 messages May 1 – May 4

Subsystems (2)

Stable branch EROFS file system

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[email protected]

author maintainer

2026-05-01 10:58 UTC #0 lore raw

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x d18a3b5d337fa412a38e776e6b4b857a58836575
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026050132-undercoat-undercoat-0f5b@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From d18a3b5d337fa412a38e776e6b4b857a58836575 Mon Sep 17 00:00:00 2001
From: Gao Xiang <[email protected]>
Date: Tue, 21 Apr 2026 15:59:52 +0800
Subject: [PATCH] erofs: fix the out-of-bounds nameoff handling for trailing
dirents

Currently we already have boundary-checks for nameoffs, but the trailing dirents are special since the namelens are calculated with strnlen() with unchecked nameoffs.

If a crafted EROFS has a trailing dirent with nameoff >= maxsize, maxsize - nameoff can underflow, causing strnlen() to read past the directory block.

nameoff0 should also be verified to be a multiple of sizeof(struct erofs_dirent) as well [1].

[1] https://sashiko.dev/#/patchset/20260416063511.3173774-1-hsiangkao%40linux.alibaba.com

Fixes 3aa8ec716e52 ("staging: erofs: add directory operations")

Fixes 33bac912840f ("staging: erofs: keep corrupted fs from crashing kernel in erofs_readdir()")

Reported-by Yuhao Jiang <[email protected]>

Reported-by Junrui Luo <[email protected]>

Closes https://lore.kernel.org/r/[email protected] open here

Cc [email protected]

Signed-off-by Gao Xiang <[email protected]>

Reviewed-by Chao Yu <[email protected]>

fs/erofs/dir.c +15 ~~-13~~

index e5132575b9d3..4aa52a5f204a 100644
@@ -19,20 +19,18 @@ static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
 		const char *de_name = (char *)dentry_blk + nameoff;
 		unsigned int de_namelen;
 
-		/* the last dirent in the block? */
-		if (de + 1 >= end)
-			de_namelen = strnlen(de_name, maxsize - nameoff);
-		else
+		/* non-trailing dirent in the directory block? */
+		if (de + 1 < end)
 			de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;
+		else if (maxsize <= nameoff)
+			goto err_bogus;
+		else
+			de_namelen = strnlen(de_name, maxsize - nameoff);
 
-		/* a corrupted entry is found */
-		if (nameoff + de_namelen > maxsize ||
-		    de_namelen > EROFS_NAME_LEN) {
-			erofs_err(dir->i_sb, "bogus dirent @ nid %llu",
-				  EROFS_I(dir)->nid);
-			DBG_BUGON(1);
-			return -EFSCORRUPTED;
-		}
+		/* a corrupted entry is found (including negative namelen) */
+		if (!in_range32(de_namelen, 1, EROFS_NAME_LEN) ||
+		    nameoff + de_namelen > maxsize)
+			goto err_bogus;
 
 		if (!dir_emit(ctx, de_name, de_namelen,
 			      erofs_nid_to_ino64(EROFS_SB(dir->i_sb),

@@ -42,6 +40,10 @@ static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
 		ctx->pos += sizeof(struct erofs_dirent);
 	}
 	return 0;
+err_bogus:
+	erofs_err(dir->i_sb, "bogus dirent @ nid %llu", EROFS_I(dir)->nid);
+	DBG_BUGON(1);
+	return -EFSCORRUPTED;
 }
 
 static int erofs_readdir(struct file *f, struct dir_context *ctx)

@@ -88,7 +90,7 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
 		}
 
 		nameoff = le16_to_cpu(de->nameoff);
-		if (nameoff < sizeof(struct erofs_dirent) || nameoff >= bsz) {
+		if (!nameoff || nameoff >= bsz || (nameoff % sizeof(*de))) {
 			erofs_err(sb, "invalid de[0].nameoff %u @ nid %llu",
 				  nameoff, EROFS_I(dir)->nid);
 			err = -EFSCORRUPTED;

Sasha Levin

maintainer

2026-05-01 18:48 UTC #1 lore raw

PATCH 1/1 erofs: fix the out-of-bounds nameoff handling for trailing dirents

From: Gao Xiang <[email protected]>

[ Upstream commit d18a3b5d337fa412a38e776e6b4b857a58836575 ]

Currently we already have boundary-checks for nameoffs, but the trailing dirents are special since the namelens are calculated with strnlen() with unchecked nameoffs.

If a crafted EROFS has a trailing dirent with nameoff >= maxsize, maxsize - nameoff can underflow, causing strnlen() to read past the directory block.

nameoff0 should also be verified to be a multiple of sizeof(struct erofs_dirent) as well [1].

[1] https://sashiko.dev/#/patchset/20260416063511.3173774-1-hsiangkao%40linux.alibaba.com

Fixes 3aa8ec716e52 ("staging: erofs: add directory operations")

Fixes 33bac912840f ("staging: erofs: keep corrupted fs from crashing kernel in erofs_readdir()")

Reported-by Yuhao Jiang <[email protected]>

Reported-by Junrui Luo <[email protected]>

Closes https://lore.kernel.org/r/[email protected] open here

Cc [email protected]

Signed-off-by Gao Xiang <[email protected]>

Reviewed-by Chao Yu <[email protected]>

[ replaced upstream `bsz` with `PAGE_SIZE` and `sizeof(*de)` with `sizeof(struct erofs_dirent)` ]

Signed-off-by Sasha Levin <[email protected]>

---
 fs/erofs/dir.c | 30 ++++++++++++++++--------------
 1 file changed, 16 insertions(+), 14 deletions(-)

fs/erofs/dir.c +16 ~~-14~~

index eee9b0b31b639..ac140587505b5 100644
@@ -37,20 +37,18 @@ static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
 		nameoff = le16_to_cpu(de->nameoff);
 		de_name = (char *)dentry_blk + nameoff;
 
-		/* the last dirent in the block? */
-		if (de + 1 >= end)
-			de_namelen = strnlen(de_name, maxsize - nameoff);
-		else
+		/* non-trailing dirent in the directory block? */
+		if (de + 1 < end)
 			de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;
+		else if (maxsize <= nameoff)
+			goto err_bogus;
+		else
+			de_namelen = strnlen(de_name, maxsize - nameoff);
 
-		/* a corrupted entry is found */
-		if (nameoff + de_namelen > maxsize ||
-		    de_namelen > EROFS_NAME_LEN) {
-			erofs_err(dir->i_sb, "bogus dirent @ nid %llu",
-				  EROFS_I(dir)->nid);
-			DBG_BUGON(1);
-			return -EFSCORRUPTED;
-		}
+		/* a corrupted entry is found (including negative namelen) */
+		if (!in_range32(de_namelen, 1, EROFS_NAME_LEN) ||
+		    nameoff + de_namelen > maxsize)
+			goto err_bogus;
 
 		debug_one_dentry(d_type, de_name, de_namelen);
 		if (!dir_emit(ctx, de_name, de_namelen,

@@ -62,6 +60,10 @@ static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
 	}
 	*ofs = maxsize;
 	return 0;
+err_bogus:
+	erofs_err(dir->i_sb, "bogus dirent @ nid %llu", EROFS_I(dir)->nid);
+	DBG_BUGON(1);
+	return -EFSCORRUPTED;
 }
 
 static int erofs_readdir(struct file *f, struct dir_context *ctx)

@@ -95,8 +97,8 @@ static int erofs_readdir(struct file *f, struct dir_context *ctx)
 
 		nameoff = le16_to_cpu(de->nameoff);
 
-		if (nameoff < sizeof(struct erofs_dirent) ||
-		    nameoff >= PAGE_SIZE) {
+		if (!nameoff || nameoff >= PAGE_SIZE ||
+		    (nameoff % sizeof(struct erofs_dirent))) {
 			erofs_err(dir->i_sb,
 				  "invalid de[0].nameoff %u @ nid %llu",
 				  nameoff, EROFS_I(dir)->nid);

Signature · 1 line

2.53.0

Gao Xiang

2026-05-04 09:37 UTC #2 lore raw

Re: [PATCH 5.15.y] erofs: fix the out-of-bounds nameoff handling for trailing dirents

Quoted 17 lines · Sasha Levin

From: Gao Xiang <[email protected]>
[ Upstream commit d18a3b5d337fa412a38e776e6b4b857a58836575 ]
Currently we already have boundary-checks for nameoffs, but the trailing dirents are special since the namelens are calculated with strnlen() with unchecked nameoffs.
If a crafted EROFS has a trailing dirent with nameoff >= maxsize, maxsize - nameoff can underflow, causing strnlen() to read past the directory block.
nameoff0 should also be verified to be a multiple of sizeof(struct erofs_dirent) as well [1].
[1] https://sashiko.dev/#/patchset/20260416063511.3173774-1-hsiangkao%40linux.alibaba.com

Quoted 10 lines

Fixes 3aa8ec716e52 ("staging: erofs: add directory operations")
Fixes 33bac912840f ("staging: erofs: keep corrupted fs from crashing kernel in erofs_readdir()")
Reported-by Yuhao Jiang <[email protected]>
Reported-by Junrui Luo <[email protected]>
Closes https://lore.kernel.org/r/[email protected] open here
Cc [email protected]
Signed-off-by Gao Xiang <[email protected]>
Reviewed-by Chao Yu <[email protected]>
[ replaced upstream `bsz` with `PAGE_SIZE` and `sizeof(*de)` with `sizeof(struct erofs_dirent)` ]
Signed-off-by Sasha Levin <[email protected]>

Looks good to me.

Thanks,
Gao Xiang