fs/ntfs3: fix KMSAN uninit-value in ni_create_attr_list

The call to kmalloc() to allocate the attribute list buffer is given a size of al_aligned(rs). This size can be larger than the data subsequently copied into the buffer, leaving trailing bytes uninitialized.

This can trigger a KMSAN "uninit-value" warning if that memory is later accessed.

Fix this by using kzalloc() instead, which ensures the entire allocated buffer is zero-initialized, preventing the warning.

Reported-by [email protected]

Closes https://syzkaller.appspot.com/bug?extid=83c9dd5c0dcf6184fdbf

Signed-off-by Nirbhay Sharma <[email protected]>

---
The following syzbot test commands were used to verify the fix against both linux-next and a specific mainline commit. Both kernels were configured with CONFIG_KMSAN=y, and no KMSAN warnings were observed with the patch applied.

An attempt to test against the latest mainline tip failed due to an unrelated boot failure in the SCSI subsystem (KMSAN: use-after-free in scsi_get_vpd_buf). Therefore, testing was done on the last known-good mainline commit below.

For mainline commit 9b0d551bcc05 ("Merge tag 'pull-misc' of..."):
#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 9b0d551bcc05

For the linux-next branch:
#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master

  fs/ntfs3/frecord.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

fs/ntfs3/frecord.c +0 -0

index 8f9fe1d7a690..4fe8da7fc034 100644

Quoted 38 lines · Nirbhay Sharma

The call to kmalloc() to allocate the attribute list buffer is given a size of al_aligned(rs). This size can be larger than the data subsequently copied into the buffer, leaving trailing bytes uninitialized.

This can trigger a KMSAN "uninit-value" warning if that memory is later accessed.

Fix this by using kzalloc() instead, which ensures the entire allocated buffer is zero-initialized, preventing the warning.

Reported-by [email protected]

Closes https://syzkaller.appspot.com/bug?extid=83c9dd5c0dcf6184fdbf

Signed-off-by Nirbhay Sharma <[email protected]>

---
The following syzbot test commands were used to verify the fix against both linux-next and a specific mainline commit. Both kernels were configured with CONFIG_KMSAN=y, and no KMSAN warnings were observed with the patch applied.

An attempt to test against the latest mainline tip failed due to an unrelated boot failure in the SCSI subsystem (KMSAN: use-after-free in scsi_get_vpd_buf). Therefore, testing was done on the last known-good mainline commit below.

For mainline commit 9b0d551bcc05 ("Merge tag 'pull-misc' of..."):
#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 9b0d551bcc05

For the linux-next branch:
#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master

  fs/ntfs3/frecord.c | 2 +-

  1 file changed, 1 insertion(+), 1 deletion(-)

fs/ntfs3/frecord.c +0 -0

index 8f9fe1d7a690..4fe8da7fc034 100644

fs/ntfs3/frecord.c int ni_create_attr_list(struct ntfs_inode *ni) · line 772

Quoted 7 lines

fs/ntfs3/frecord.c +1 -1

@@ -767,7 +767,7 @@ int ni_create_attr_list(struct ntfs_inode *ni)
        * Skip estimating exact memory requirement.
        * Looks like one record_size is always enough.
        */
-    le = kmalloc(al_aligned(rs), GFP_NOFS);
+    le = kzalloc(al_aligned(rs), GFP_NOFS);
       if (!le)
           return -ENOMEM;

Hi Konstantin,

I sent this patch about 3 weeks ago and haven't heard back yet. I wanted to check if there are any concerns with the patch or if any changes are needed. The fix addresses a KMSAN uninit-value bug and has been tested successfully on both linux-next and the commit from the syzbot report.

Please let me know if you need any additional information or testing.

Thanks,
Nirbhay