FAILED: patch "[PATCH] ntfs3: validate split-point offset in indx_insert_into_buffer" failed to apply to 5.15-stable tree

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 f1df9d771df47aa40de6d70949c28720ae1e430d
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026072049-legroom-strode-957e@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

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

From f1df9d771df47aa40de6d70949c28720ae1e430d Mon Sep 17 00:00:00 2001
From: Michael Bommarito <[email protected]>
Date: Fri, 17 Apr 2026 18:57:12 -0400
Subject: [PATCH] ntfs3: validate split-point offset in indx_insert_into_buffer

indx_insert_into_buffer() computes

    used = used1 - to_copy - sp_size;
    memmove(de_t, Add2Ptr(sp, sp_size), used - le32_to_cpu(hdr1->de_off));

where sp and sp_size come from hdr_find_split(). hdr_find_split() walks entries by le16_to_cpu(e->size) without validating that each step stays within hdr->used or that the size field is at least sizeof(struct NTFS_DE). index_hdr_check(), the on-load gatekeeper, only validates header-level fields (used, total, de_off) and does not walk per-entry sizes.

A crafted NTFS image whose leaf INDEX_HDR reports used == total but contains one interior NTFS_DE with size = 0xFFF0 therefore passes validation, descends to indx_insert_into_buffer() through the ntfs_create() -> indx_insert_entry() path, and makes hdr_find_split() return an sp whose sp_size (0xFFF0) greatly exceeds the remaining bytes in the buffer. The u32 subtraction underflows and the memmove count becomes a near-4-GiB value, producing an out-of-bounds kernel write that corrupts adjacent allocations and panics the kernel.

Reproduced on 7.0.0-rc7 with UML + KASAN via a crafted image and a single 'touch' inside the mounted directory; crash site resolves to fs/ntfs3/index.c at the memmove. Trigger requires only local mount of an attacker-supplied filesystem image (USB, loopback, or removable media auto-mount).

Reject the split whenever the chosen sp plus its declared size already extends past hdr1->used. This is the minimal fix; it preserves the existing hdr_find_split() contract and relies on the same out: cleanup path as the pre-existing error returns.

A prior OOB read in the very same indx_insert_into_buffer() memmove was fixed in commit b8c44949044e ("fs/ntfs3: Fix OOB read in indx_insert_into_buffer") by tightening hdr_find_e(), but that fix does not cover the split-point size field path addressed here: sp is returned by hdr_find_split(), not hdr_find_e(), and the underflow is driven by sp->size rather than hdr->used exceeding hdr->total.

index 5868964e129c..ade276225999 100644
@@ -1862,6 +1862,20 @@ indx_insert_into_buffer(struct ntfs_index *indx, struct ntfs_inode *ni,
 	memcpy(up_e, sp, sp_size);
 
 	used1 = le32_to_cpu(hdr1->used);
+
+	/*
+	 * hdr_find_split does not validate per-entry sizes, so a crafted
+	 * NTFS_DE whose le16 size field is out of range can place sp such
+	 * that (PtrOffset(hdr1, sp) + sp_size) exceeds used1. Without this
+	 * guard the u32 'used = used1 - to_copy - sp_size' underflows and
+	 * the subsequent memmove count becomes a near-4-GiB value,
+	 * triggering an out-of-bounds kernel write.
+	 */
+	if (PtrOffset(hdr1, sp) + sp_size > used1) {
+		err = -EINVAL;
+		goto out;
+	}
+
 	hdr1_saved = kmemdup(hdr1, used1, GFP_NOFS);
 	if (!hdr1_saved) {
 		err = -ENOMEM;

From: Konstantin Komarov <[email protected]>

[ Upstream commit 63e92a0c5a0d5816803907a3e30a91ef72c903a5 ]

Affect xfstest 320.

Stable-dep-of: f1df9d771df4 ("ntfs3: validate split-point offset in indx_insert_into_buffer")

---
 fs/ntfs3/index.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

index b0aa5cc63b5079..80fc3f61f81484 100644
@@ -1803,10 +1803,11 @@ indx_insert_into_buffer(struct ntfs_index *indx, struct ntfs_inode *ni,
 	struct indx_node *n1 = fnd->nodes[level];
 	struct INDEX_HDR *hdr1 = &n1->index->ihdr;
 	struct INDEX_HDR *hdr2;
-	u32 to_copy, used;
+	u32 to_copy, used, used1;
 	CLST new_vbn;
 	__le64 t_vbn, *sub_vbn;
 	u16 sp_size;
+	void *hdr1_saved = NULL;
 
 	/* Try the most easy case. */
 	e = fnd->level - 1 == level ? fnd->de[level] : NULL;

@@ -1839,6 +1840,13 @@ indx_insert_into_buffer(struct ntfs_index *indx, struct ntfs_inode *ni,
 		return -ENOMEM;
 	memcpy(up_e, sp, sp_size);
 
+	used1 = le32_to_cpu(hdr1->used);
+	hdr1_saved = kmemdup(hdr1, used1, GFP_NOFS);
+	if (!hdr1_saved) {
+		err = -ENOMEM;
+		goto out;
+	}
+
 	if (!hdr1->flags) {
 		up_e->flags |= NTFS_IE_HAS_SUBNODES;
 		up_e->size = cpu_to_le16(sp_size + sizeof(u64));

@@ -1871,7 +1879,7 @@ indx_insert_into_buffer(struct ntfs_index *indx, struct ntfs_inode *ni,
 	hdr_insert_head(hdr2, de_t, to_copy);
 
 	/* Remove all entries (sp including) from hdr1. */
-	used = le32_to_cpu(hdr1->used) - to_copy - sp_size;
+	used = used1 - to_copy - sp_size;
 	memmove(de_t, Add2Ptr(sp, sp_size), used - le32_to_cpu(hdr1->de_off));
 	hdr1->used = cpu_to_le32(used);
 

@@ -1901,8 +1909,6 @@ indx_insert_into_buffer(struct ntfs_index *indx, struct ntfs_inode *ni,
 	if (!level) {
 		/* Insert in root. */
 		err = indx_insert_into_root(indx, ni, up_e, NULL, ctx, fnd, 0);
-		if (err)
-			goto out;
 	} else {
 		/*
 		 * The target buffer's parent is another index buffer.

@@ -1910,12 +1916,20 @@ indx_insert_into_buffer(struct ntfs_index *indx, struct ntfs_inode *ni,
 		 */
 		err = indx_insert_into_buffer(indx, ni, root, up_e, ctx,
 					      level - 1, fnd);
-		if (err)
-			goto out;
+	}
+
+	if (err) {
+		/*
+		 * Undo critical operations.
+		 */
+		indx_mark_free(indx, ni, new_vbn >> indx->idx2vbn_bits);
+		memcpy(hdr1, hdr1_saved, used1);
+		indx_write(indx, ni, n1, 0);
 	}
 
 out:
 	kfree(up_e);
+	kfree(hdr1_saved);
 
 	return err;
 }

@@ -1974,16 +1988,12 @@ int indx_insert_entry(struct ntfs_index *indx, struct ntfs_inode *ni,
 		 */
 		err = indx_insert_into_root(indx, ni, new_de, fnd->root_de, ctx,
 					    fnd, undo);
-		if (err)
-			goto out;
 	} else {
 		/*
 		 * Found a leaf buffer, so we'll insert the new entry into it.
 		 */
 		err = indx_insert_into_buffer(indx, ni, root, new_de, ctx,
 					      fnd->level - 1, fnd);
-		if (err)
-			goto out;
 	}
 
 out:

2.53.0

From: Michael Bommarito <[email protected]>

[ Upstream commit f1df9d771df47aa40de6d70949c28720ae1e430d ]

indx_insert_into_buffer() computes

    used = used1 - to_copy - sp_size;
    memmove(de_t, Add2Ptr(sp, sp_size), used - le32_to_cpu(hdr1->de_off));

where sp and sp_size come from hdr_find_split(). hdr_find_split() walks entries by le16_to_cpu(e->size) without validating that each step stays within hdr->used or that the size field is at least sizeof(struct NTFS_DE). index_hdr_check(), the on-load gatekeeper, only validates header-level fields (used, total, de_off) and does not walk per-entry sizes.

A crafted NTFS image whose leaf INDEX_HDR reports used == total but contains one interior NTFS_DE with size = 0xFFF0 therefore passes validation, descends to indx_insert_into_buffer() through the ntfs_create() -> indx_insert_entry() path, and makes hdr_find_split() return an sp whose sp_size (0xFFF0) greatly exceeds the remaining bytes in the buffer. The u32 subtraction underflows and the memmove count becomes a near-4-GiB value, producing an out-of-bounds kernel write that corrupts adjacent allocations and panics the kernel.

Reproduced on 7.0.0-rc7 with UML + KASAN via a crafted image and a single 'touch' inside the mounted directory; crash site resolves to fs/ntfs3/index.c at the memmove. Trigger requires only local mount of an attacker-supplied filesystem image (USB, loopback, or removable media auto-mount).

Reject the split whenever the chosen sp plus its declared size already extends past hdr1->used. This is the minimal fix; it preserves the existing hdr_find_split() contract and relies on the same out: cleanup path as the pre-existing error returns.

A prior OOB read in the very same indx_insert_into_buffer() memmove was fixed in commit b8c44949044e ("fs/ntfs3: Fix OOB read in indx_insert_into_buffer") by tightening hdr_find_e(), but that fix does not cover the split-point size field path addressed here: sp is returned by hdr_find_split(), not hdr_find_e(), and the underflow is driven by sp->size rather than hdr->used exceeding hdr->total.

---
 fs/ntfs3/index.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

index 80fc3f61f81484..4285a7302acb07 100644
@@ -1841,6 +1841,20 @@ indx_insert_into_buffer(struct ntfs_index *indx, struct ntfs_inode *ni,
 	memcpy(up_e, sp, sp_size);
 
 	used1 = le32_to_cpu(hdr1->used);
+
+	/*
+	 * hdr_find_split does not validate per-entry sizes, so a crafted
+	 * NTFS_DE whose le16 size field is out of range can place sp such
+	 * that (PtrOffset(hdr1, sp) + sp_size) exceeds used1. Without this
+	 * guard the u32 'used = used1 - to_copy - sp_size' underflows and
+	 * the subsequent memmove count becomes a near-4-GiB value,
+	 * triggering an out-of-bounds kernel write.
+	 */
+	if (PtrOffset(hdr1, sp) + sp_size > used1) {
+		err = -EINVAL;
+		goto out;
+	}
+
 	hdr1_saved = kmemdup(hdr1, used1, GFP_NOFS);
 	if (!hdr1_saved) {
 		err = -ENOMEM;

2.53.0