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smb: client: fix ALIGN() overflow in symlink_data() error context loop

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The check added by commit 7d9a7f1f96 ("smb/client: fix possible
infinite loop and oob read in symlink_data()") compared the post-ALIGN
length against the remaining buffer, but ALIGN() itself can overflow:
for ErrorDataLength near UINT32_MAX (e.g. 0xFFFFFFF9), ALIGN(x, 8)
wraps to 0, so the subsequent bounds check passes, and the loop
advances by zero bytes leaving 'p' pointing into stale data.

Fix by checking the raw ErrorDataLength against the remaining space
before applying ALIGN(), then checking again after.  Since raw_len is
bounded by the buffer, raw_len + 7 cannot overflow, so the second check
is an exact post-alignment bounds guard.

Fixes: 76894f3e2f ("cifs: improve symlink handling for smb2+")
Cc: stable@vger.kernel.org
Signed-off-by: Frank Sorenson <sorenson@redhat.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
This commit is contained in:
Frank Sorenson
2026-08-17 12:16:51 -05:00
committed by Paulo Alcantara
parent 3fffaa8a64
commit 62656b024e
1 changed files with 4 additions and 1 deletions
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5
fs/smb/client/smb2file.c
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@@ -61,7 +61,10 @@ static struct smb2_symlink_err_rsp *symlink_data(const struct kvec *iov)
cifs_dbg(FYI, "%s: skipping unhandled error context: 0x%x\n",
__func__, le32_to_cpu(p->ErrorId));
len = ALIGN(le32_to_cpu(p->ErrorDataLength), 8);
len = le32_to_cpu(p->ErrorDataLength);
if (len > end - ((u8 *)p + sizeof(*p)))
return ERR_PTR(-EINVAL);
len = ALIGN(len, 8);
if (len > end - ((u8 *)p + sizeof(*p)))
return ERR_PTR(-EINVAL);