FAILED: patch "[PATCH] fs/ntfs3: validate the EA value length in ntfs_read_ea()" failed to apply to 6.6-stable tree

FAILED: patch "[PATCH] fs/ntfs3: validate the EA value length in ntfs_read_ea()" failed to apply to 6.6-stable tree

[Sasha Levin]

The patch below does not apply to the 6.6-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 <stable@vger.kernel.org>.

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-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 351817226fbf0031c4c63d1f5d7f15c3172312eb
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107054019-failed-6.6-351817226fbf@kernel.org' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Thanks,
Sasha

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

From 351817226fbf0031c4c63d1f5d7f15c3172312eb Mon Sep 17 00:00:00 2001
From: Yuejie Shi <syjcnss@gmail.com>
Date: Mon, 3 Aug 2026 12:34:32 +0800
Subject: [PATCH] fs/ntfs3: validate the EA value length in ntfs_read_ea()

ntfs_read_ea() checks the $EA list for consistency, but it only
recomputes the packed size of an entry when the entry's own size field is
zero:

	for (off = 0; off < size; off += ea_size) {
		const struct EA_FULL *ef = Add2Ptr(ea_p, off);
		u32 bytes = size - off;
		...
		if (ef->size) {
			ea_size = le32_to_cpu(ef->size);
			if (ea_size > bytes)
				goto out1;
			continue;              /* <- elength never checked */
		}
		...
		ea_size = ALIGN(struct_size(ef, name,
					    1 + ef->name_len +
						    le16_to_cpu(ef->elength)),
				4);
		if (ea_size > bytes)
			goto out1;
	}

ef->size is non-zero for every entry except the last one, and it is what
ntfs3 itself writes (ntfs_set_ea() stores exactly that aligned packed
size), so in practice elength is not validated at all.  find_ea() then
uses unpacked_ea_size(), which also prefers ea->size when it is set, so
it agrees and hands the entry back.

ntfs_get_ea() copies elength bytes with no further bound of its own:

	len = le16_to_cpu(ea->elength);
	...
	if (len > size) {              /* size is the *caller's* buffer */
		err = -ERANGE;
		...
	}
	memcpy(buffer, ea->name + ea->name_len + 1, len);

so a caller that supplies a large enough buffer receives up to 64 KiB of
whatever follows the small $EA allocation -- straight to userspace via
getxattr(2).

Compute the packed size unconditionally and require it to fit in the
entry.  Hoist the "bytes < offsetof(struct EA_FULL, name)" test above the
ef->size branch as well: name_len and elength were being read there
without it, which is itself a small over-read of the kmalloc'd buffer
when fewer than 8 bytes are left.  The old "bytes < sizeof(ef->size)"
test is subsumed by it.

  # mkntfs image; create /mnt/ntfs/poc with user.ntfs6 set, then rewrite
  # that EA_FULL's elength from 0xf to 0xff00 on the raw device
  mount -t ntfs3 -o ro /dev/vda /mnt/ntfs
  getxattr("/mnt/ntfs/poc", "user.ntfs6", buf, 128 * 1024);

  BUG: KASAN: slab-out-of-bounds in ntfs_get_ea+0x294/0x3e0
  Read of size 65280 at addr ffff0000cca53acf by task xattr_probe/142
   __asan_memcpy+0x3c/0xa0
   ntfs_get_ea+0x294/0x3e0
   ntfs_getxattr+0x284/0x318
   __vfs_getxattr+0x104/0x160
   vfs_getxattr+0x1b4/0x1e0
   do_getxattr+0xcc/0x230
   path_getxattrat+0x184/0x270
   __arm64_sys_getxattr+0x64/0x80
  Allocated by task 142:
   __kmalloc_noprof+0x294/0x668
   ntfs_read_ea+0x1e4/0x420
   ntfs_get_ea+0x2c8/0x3e0
  The buggy address belongs to the object at ffff0000cca53a80
   which belongs to the cache kmalloc-96 of size 96

The object being over-read is the one ntfs_read_ea() just allocated, and
it is 96 bytes.

Entries written by ntfs3 and by Windows set size to the aligned packed
size, so the new test does not reject anything a working filesystem
produces.

Fixes: be71b5cba2e6 ("fs/ntfs3: Add attrib operations")
Cc: stable@vger.kernel.org
Signed-off-by: Yuejie Shi <syjcnss@gmail.com>
[almaz.alexandrovich@paragon-software.com: applied as-is, logic is the same but the code is cleaner]
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
---
 fs/ntfs3/xattr.c | 45 ++++++++++++++-------------------------------
 1 file changed, 14 insertions(+), 31 deletions(-)

diff --git a/fs/ntfs3/xattr.c b/fs/ntfs3/xattr.c
index d6ad06415318d..e1fa58aa03611 100644
--- a/fs/ntfs3/xattr.c
+++ b/fs/ntfs3/xattr.c
@@ -146,49 +146,32 @@ static int ntfs_read_ea(struct ntfs_inode *ni, struct EA_FULL **ea,
 	for (off = 0; off < size; off += ea_size) {
 		const struct EA_FULL *ef = Add2Ptr(ea_p, off);
 		u32 bytes = size - off;
-		size_t need;
-
-		/* Check if we can use field ea->size. */
-		if (bytes < sizeof(ef->size))
-			goto out1;
+		u32 packed_size;
 
 		/* Check if we can use fields ef->name_len and ef->elength. */
 		if (bytes < offsetof(struct EA_FULL, name))
 			goto out1;
 
-		/* Size needed to hold this record's name and value. */
-		need = struct_size(ef, name,
-				   1 + ef->name_len + le16_to_cpu(ef->elength));
+		/*
+		 * The name and the value have to fit in the entry whether or
+		 * not ef->size is set, because ntfs_get_ea() copies elength
+		 * bytes out of this buffer and checks them only against the
+		 * caller supplied buffer size.
+		 */
+		packed_size =
+			ALIGN(struct_size(ef, name,
+					  1 + ef->name_len +
+						  le16_to_cpu(ef->elength)),
+			      4);
 
 		if (ef->size) {
 			ea_size = le32_to_cpu(ef->size);
-			/* ef->size must fit the list and cover the record. */
-			if (ea_size > bytes || ea_size < need)
-				goto out1;
-			if (bytes < offsetof(struct EA_FULL, name))
-				goto out1;
-
-			/* Check if we can use fields ef->name_len and ef->elength. */
-			if (bytes < offsetof(struct EA_FULL, name))
-				goto out1;
-
-			/*
-			 * The declared entry size (ef->size) must be large
-			 * enough to hold the name and value.  Otherwise a later
-			 * reader such as ntfs_get_ea() copies ef->elength bytes
-			 * starting past the entry, reading out of bounds of the
-			 * ea buffer and leaking adjacent heap memory to
-			 * userspace via getxattr().
-			 */
-			if (struct_size(ef, name,
-					1 + ef->name_len +
-						le16_to_cpu(ef->elength)) >
-			    ea_size)
+			if (ea_size > bytes || packed_size > ea_size)
 				goto out1;
 			continue;
 		}
 
-		ea_size = ALIGN(need, 4);
+		ea_size = packed_size;
 		if (ea_size > bytes)
 			goto out1;
 	}
-- 
2.53.0

[PATCH 6.6.y 1/3] fs/ntfs3: validate EA entry layout against ef->size in ntfs_read_ea

[Sasha Levin]

From: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

[ Upstream commit 01e56820ef52d14a5560fb7c0c6f2f75ef6f9393 ]

In ntfs_read_ea(), the ef->size branch only checks that the declared
entry size fits the remaining buffer; unlike the zero-size branch it
never verifies that the entry's own name and value fit inside ef->size.
A crafted image can thus present an in-bounds ef->size with an arbitrary
elength, which find_ea()/ntfs_get_ea() later use as the memcpy length,
reading past the allocation and leaking adjacent heap memory:

  BUG: KASAN: slab-out-of-bounds in ntfs_get_ea (fs/ntfs3/xattr.c:302)
  Read of size 65535 at addr ffff888010770b0f by task exploit/142
   ...
   __asan_memcpy (mm/kasan/shadow.c:105)
   ntfs_get_ea (fs/ntfs3/xattr.c:302)
   ntfs_getxattr (fs/ntfs3/xattr.c:848)
   __vfs_getxattr (fs/xattr.c:446)
   vfs_getxattr (fs/xattr.c:479)
   do_getxattr (fs/xattr.c:808)
   filename_getxattr (fs/xattr.c:837)
   path_getxattrat (fs/xattr.c:876)
   do_syscall_64 (arch/x86/entry/syscall_64.c:94)
  ...
  The buggy address is located 15 bytes inside of
   allocated 20-byte region, cache kmalloc-32

Validate the name/value layout in the ef->size branch too, bounding it
against ef->size, as the zero-size branch validates it against the
buffer.

Fixes: be71b5cba2e6 ("fs/ntfs3: Add attrib operations")
Reported-by: Weiming Shi <bestswngs@gmail.com>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Xiang Mei <xmei5@asu.edu>
[almaz.alexandrovich@paragon-software.com: remove duplicate check of need > ea_size]
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Stable-dep-of: 351817226fbf ("fs/ntfs3: validate the EA value length in ntfs_read_ea()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/ntfs3/xattr.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/ntfs3/xattr.c b/fs/ntfs3/xattr.c
index 30d5b8b53974d..1e4ad309423f5 100644
--- a/fs/ntfs3/xattr.c
+++ b/fs/ntfs3/xattr.c
@@ -165,6 +165,8 @@ static int ntfs_read_ea(struct ntfs_inode *ni, struct EA_FULL **ea,
 			/* ef->size must fit the list and cover the record. */
 			if (ea_size > bytes || ea_size < need)
 				goto out1;
+			if (bytes < offsetof(struct EA_FULL, name))
+				goto out1;
 			continue;
 		}
 
-- 
2.53.0

[PATCH 6.6.y 2/3] fs/ntfs3: validate that EA entry size covers its name and value

[Sasha Levin]

From: Aldo Ariel Panzardo <qwe.aldo@gmail.com>

[ Upstream commit 60bd50014cc9a97c5e34a8bddd2bad4d2dc5acb7 ]

ntfs_read_ea() walks the on-disk $EA attribute and checks each EA_FULL
entry for consistency.  For an entry with a non-zero ef->size (the
offset to the next entry) the loop only verifies that this stride fits
in the remaining buffer, and then continues:

	if (ef->size) {
		ea_size = le32_to_cpu(ef->size);
		if (ea_size > bytes)
			goto out1;
		continue;
	}

It never verifies that the entry's own name (ef->name_len) and value
(ef->elength) actually fit inside ef->size.  A later reader trusts
ef->elength unconditionally; ntfs_get_ea() does:

	len = le16_to_cpu(ea->elength);		/* up to 0xffff */
	...
	if (len > size)				/* size is the user buffer */
		return -ERANGE;
	memcpy(buffer, ea->name + ea->name_len + 1, len);

A crafted image with a small but valid ef->size (e.g. 24) and
ef->elength == 0xffff therefore passes validation, and a getxattr()
with a large enough user buffer copies up to 64 KiB starting just past
the short entry -- an out-of-bounds read of the ea_all allocation that
leaks adjacent kernel heap memory to userspace.

  BUG: KASAN: slab-out-of-bounds in ntfs_get_ea+0x2b8/0x3f0
  Read of size 65535 ...
   ntfs_get_ea -> ntfs_getxattr -> vfs_getxattr -> do_getxattr

The zero-ef->size branch already computes the same struct_size() to
derive the stride; mirror that in the non-zero branch and reject the
entry when its declared size cannot hold the name and value.

Fixes: 0e8235d28f3a ("fs/ntfs3: Check fields while reading")
Cc: stable@vger.kernel.org
Signed-off-by: Aldo Ariel Panzardo <qwe.aldo@gmail.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Stable-dep-of: 351817226fbf ("fs/ntfs3: validate the EA value length in ntfs_read_ea()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/ntfs3/xattr.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/fs/ntfs3/xattr.c b/fs/ntfs3/xattr.c
index 1e4ad309423f5..5af61c90cc234 100644
--- a/fs/ntfs3/xattr.c
+++ b/fs/ntfs3/xattr.c
@@ -167,6 +167,24 @@ static int ntfs_read_ea(struct ntfs_inode *ni, struct EA_FULL **ea,
 				goto out1;
 			if (bytes < offsetof(struct EA_FULL, name))
 				goto out1;
+
+			/* Check if we can use fields ef->name_len and ef->elength. */
+			if (bytes < offsetof(struct EA_FULL, name))
+				goto out1;
+
+			/*
+			 * The declared entry size (ef->size) must be large
+			 * enough to hold the name and value.  Otherwise a later
+			 * reader such as ntfs_get_ea() copies ef->elength bytes
+			 * starting past the entry, reading out of bounds of the
+			 * ea buffer and leaking adjacent heap memory to
+			 * userspace via getxattr().
+			 */
+			if (struct_size(ef, name,
+					1 + ef->name_len +
+						le16_to_cpu(ef->elength)) >
+			    ea_size)
+				goto out1;
 			continue;
 		}
 
-- 
2.53.0

[PATCH 6.6.y 3/3] fs/ntfs3: validate the EA value length in ntfs_read_ea()

[Sasha Levin]

From: Yuejie Shi <syjcnss@gmail.com>

[ Upstream commit 351817226fbf0031c4c63d1f5d7f15c3172312eb ]

ntfs_read_ea() checks the $EA list for consistency, but it only
recomputes the packed size of an entry when the entry's own size field is
zero:

	for (off = 0; off < size; off += ea_size) {
		const struct EA_FULL *ef = Add2Ptr(ea_p, off);
		u32 bytes = size - off;
		...
		if (ef->size) {
			ea_size = le32_to_cpu(ef->size);
			if (ea_size > bytes)
				goto out1;
			continue;              /* <- elength never checked */
		}
		...
		ea_size = ALIGN(struct_size(ef, name,
					    1 + ef->name_len +
						    le16_to_cpu(ef->elength)),
				4);
		if (ea_size > bytes)
			goto out1;
	}

ef->size is non-zero for every entry except the last one, and it is what
ntfs3 itself writes (ntfs_set_ea() stores exactly that aligned packed
size), so in practice elength is not validated at all.  find_ea() then
uses unpacked_ea_size(), which also prefers ea->size when it is set, so
it agrees and hands the entry back.

ntfs_get_ea() copies elength bytes with no further bound of its own:

	len = le16_to_cpu(ea->elength);
	...
	if (len > size) {              /* size is the *caller's* buffer */
		err = -ERANGE;
		...
	}
	memcpy(buffer, ea->name + ea->name_len + 1, len);

so a caller that supplies a large enough buffer receives up to 64 KiB of
whatever follows the small $EA allocation -- straight to userspace via
getxattr(2).

Compute the packed size unconditionally and require it to fit in the
entry.  Hoist the "bytes < offsetof(struct EA_FULL, name)" test above the
ef->size branch as well: name_len and elength were being read there
without it, which is itself a small over-read of the kmalloc'd buffer
when fewer than 8 bytes are left.  The old "bytes < sizeof(ef->size)"
test is subsumed by it.

  # mkntfs image; create /mnt/ntfs/poc with user.ntfs6 set, then rewrite
  # that EA_FULL's elength from 0xf to 0xff00 on the raw device
  mount -t ntfs3 -o ro /dev/vda /mnt/ntfs
  getxattr("/mnt/ntfs/poc", "user.ntfs6", buf, 128 * 1024);

  BUG: KASAN: slab-out-of-bounds in ntfs_get_ea+0x294/0x3e0
  Read of size 65280 at addr ffff0000cca53acf by task xattr_probe/142
   __asan_memcpy+0x3c/0xa0
   ntfs_get_ea+0x294/0x3e0
   ntfs_getxattr+0x284/0x318
   __vfs_getxattr+0x104/0x160
   vfs_getxattr+0x1b4/0x1e0
   do_getxattr+0xcc/0x230
   path_getxattrat+0x184/0x270
   __arm64_sys_getxattr+0x64/0x80
  Allocated by task 142:
   __kmalloc_noprof+0x294/0x668
   ntfs_read_ea+0x1e4/0x420
   ntfs_get_ea+0x2c8/0x3e0
  The buggy address belongs to the object at ffff0000cca53a80
   which belongs to the cache kmalloc-96 of size 96

The object being over-read is the one ntfs_read_ea() just allocated, and
it is 96 bytes.

Entries written by ntfs3 and by Windows set size to the aligned packed
size, so the new test does not reject anything a working filesystem
produces.

Fixes: be71b5cba2e6 ("fs/ntfs3: Add attrib operations")
Cc: stable@vger.kernel.org
Signed-off-by: Yuejie Shi <syjcnss@gmail.com>
[almaz.alexandrovich@paragon-software.com: applied as-is, logic is the same but the code is cleaner]
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/ntfs3/xattr.c | 45 ++++++++++++++-------------------------------
 1 file changed, 14 insertions(+), 31 deletions(-)

diff --git a/fs/ntfs3/xattr.c b/fs/ntfs3/xattr.c
index 5af61c90cc234..1c18ab072987b 100644
--- a/fs/ntfs3/xattr.c
+++ b/fs/ntfs3/xattr.c
@@ -146,49 +146,32 @@ static int ntfs_read_ea(struct ntfs_inode *ni, struct EA_FULL **ea,
 	for (off = 0; off < size; off += ea_size) {
 		const struct EA_FULL *ef = Add2Ptr(ea_p, off);
 		u32 bytes = size - off;
-		size_t need;
-
-		/* Check if we can use field ea->size. */
-		if (bytes < sizeof(ef->size))
-			goto out1;
+		u32 packed_size;
 
 		/* Check if we can use fields ef->name_len and ef->elength. */
 		if (bytes < offsetof(struct EA_FULL, name))
 			goto out1;
 
-		/* Size needed to hold this record's name and value. */
-		need = struct_size(ef, name,
-				   1 + ef->name_len + le16_to_cpu(ef->elength));
+		/*
+		 * The name and the value have to fit in the entry whether or
+		 * not ef->size is set, because ntfs_get_ea() copies elength
+		 * bytes out of this buffer and checks them only against the
+		 * caller supplied buffer size.
+		 */
+		packed_size =
+			ALIGN(struct_size(ef, name,
+					  1 + ef->name_len +
+						  le16_to_cpu(ef->elength)),
+			      4);
 
 		if (ef->size) {
 			ea_size = le32_to_cpu(ef->size);
-			/* ef->size must fit the list and cover the record. */
-			if (ea_size > bytes || ea_size < need)
-				goto out1;
-			if (bytes < offsetof(struct EA_FULL, name))
-				goto out1;
-
-			/* Check if we can use fields ef->name_len and ef->elength. */
-			if (bytes < offsetof(struct EA_FULL, name))
-				goto out1;
-
-			/*
-			 * The declared entry size (ef->size) must be large
-			 * enough to hold the name and value.  Otherwise a later
-			 * reader such as ntfs_get_ea() copies ef->elength bytes
-			 * starting past the entry, reading out of bounds of the
-			 * ea buffer and leaking adjacent heap memory to
-			 * userspace via getxattr().
-			 */
-			if (struct_size(ef, name,
-					1 + ef->name_len +
-						le16_to_cpu(ef->elength)) >
-			    ea_size)
+			if (ea_size > bytes || packed_size > ea_size)
 				goto out1;
 			continue;
 		}
 
-		ea_size = ALIGN(need, 4);
+		ea_size = packed_size;
 		if (ea_size > bytes)
 			goto out1;
 	}
-- 
2.53.0