FAILED: patch "[PATCH] ksmbd: restore DACL size on check_add_overflow() to avoid" failed to apply to 7.1-stable tree

FAILED: patch "[PATCH] ksmbd: restore DACL size on check_add_overflow() to avoid" failed to apply to 7.1-stable tree

[gregkh]

The patch below does not apply to the 7.1-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-7.1.y
git checkout FETCH_HEAD
git cherry-pick -x bbf0a8e931204ecdab494a88d43b0a24a04285c5
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026072935-handyman-fascism-82fa@gregkh' --subject-prefix 'PATCH 7.1.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From bbf0a8e931204ecdab494a88d43b0a24a04285c5 Mon Sep 17 00:00:00 2001
From: Wentao Guan <guanwentao@uniontech.com>
Date: Fri, 3 Jul 2026 11:22:09 +0900
Subject: [PATCH] ksmbd: restore DACL size on check_add_overflow() to avoid
 malformed ACL

check_add_overflow() unconditionally writes the truncated sum into *d
even on overflow, per its contract in include/linux/overflow.h.
The four check_add_overflow() guards in set_posix_acl_entries_dacl()
and set_ntacl_dacl() break out of the ACE-building loops on overflow,
but the truncated *size is then consumed downstream at the end of
set_ntacl_dacl():

    pndacl->size = cpu_to_le16(le16_to_cpu(pndacl->size) + size);

This produces an on-wire NT ACL whose pndacl->size under-reports the
bytes actually written by the preceding fill_ace_for_sid()/memcpy()
calls, yielding a malformed ACL that can trigger out-of-bounds reads
when re-parsed by clients or ksmbd itself.

Restore *size to its pre-addition value on each overflow branch (via
`*size -= ace_sz` / `size -= nt_ace_size`) so that after the break,
*size once again holds the cumulative size of the successfully-written
ACEs. The committed ACL is then truncated-but-self-consistent rather
than malformed.

The ksmbd DACL builders are the only check_add_overflow() sites found
where an overflow path breaks out of a loop and the destination value
is consumed afterward. The other nearby break-style cases either
return -EINVAL on overflow (transport_ipc.c) or break without
consuming the overflowed destination value afterward (buildid.c).

Fixes: 299f962c0b02 ("ksmbd: use check_add_overflow() to prevent u16 DACL size overflow")
Assisted-by: atomcode:glm-5.2
Assisted-by: Codex:gpt-5.5
Cc: stable@vger.kernel.org
Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/smb/server/smbacl.c b/fs/smb/server/smbacl.c
index d28289188e44..f285b4f24a5b 100644
--- a/fs/smb/server/smbacl.c
+++ b/fs/smb/server/smbacl.c
@@ -663,6 +663,7 @@ static void set_posix_acl_entries_dacl(struct mnt_idmap *idmap,
 		ace_sz = fill_ace_for_sid(ntace, sid, ACCESS_ALLOWED, flags,
 				pace->e_perm, 0777);
 		if (check_add_overflow(*size, ace_sz, size)) {
+			*size -= ace_sz;
 			kfree(sid);
 			break;
 		}
@@ -677,6 +678,7 @@ static void set_posix_acl_entries_dacl(struct mnt_idmap *idmap,
 			ace_sz = fill_ace_for_sid(ntace, sid, ACCESS_ALLOWED,
 					0x03, pace->e_perm, 0777);
 			if (check_add_overflow(*size, ace_sz, size)) {
+				*size -= ace_sz;
 				kfree(sid);
 				break;
 			}
@@ -722,6 +724,7 @@ static void set_posix_acl_entries_dacl(struct mnt_idmap *idmap,
 		ace_sz = fill_ace_for_sid(ntace, sid, ACCESS_ALLOWED, 0x0b,
 				pace->e_perm, 0777);
 		if (check_add_overflow(*size, ace_sz, size)) {
+			*size -= ace_sz;
 			kfree(sid);
 			break;
 		}
@@ -765,8 +768,10 @@ static void set_ntacl_dacl(struct mnt_idmap *idmap,
 				goto next_ace;
 
 			memcpy((char *)pndace + size, ntace, nt_ace_size);
-			if (check_add_overflow(size, nt_ace_size, &size))
+			if (check_add_overflow(size, nt_ace_size, &size)) {
+				size -= nt_ace_size;
 				break;
+			}
 			num_aces++;
 
 next_ace:

[PATCH 7.1.y 1/2] ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl

[Wentao Guan]

From: Haofeng Li <lihaofeng@kylinos.cn>

set_ntacl_dacl() copies each ACE from the attacker-controlled stored
security descriptor verbatim into the response DACL without checking
sid.num_subauth. The ACE bytes (including an unchecked num_subauth)
originate from an authenticated SMB2_SET_INFO(SecInfo=DACL) that is
stored raw via ksmbd_vfs_set_sd_xattr(); parse_dacl() rejects a bad ACE
with `break` rather than an error, so parse_sec_desc() still returns
success and the malformed SD reaches the xattr intact.

On a subsequent SMB2_QUERY_INFO(SecInfo=DACL) for an inode carrying a
POSIX access ACL, build_sec_desc() -> set_ntacl_dacl() ->
set_posix_acl_entries_dacl() walks the copied ACEs and reads

    ntace->sid.sub_auth[ntace->sid.num_subauth - 1]

with num_subauth taken straight from the stored SD. Since sub_auth[]
is fixed at SID_MAX_SUB_AUTHORITIES (15), a crafted num_subauth (e.g.
255) drives an out-of-bounds heap read of ~1 KB with an offset fully
controlled by an authenticated client.

The sibling functions already gate this field:
  parse_dacl()    -- num_subauth == 0 || > SID_MAX_SUB_AUTHORITIES
  parse_sid()     -- num_subauth > SID_MAX_SUB_AUTHORITIES
  smb_copy_sid()  -- min_t(u8, num_subauth, SID_MAX_SUB_AUTHORITIES)
set_ntacl_dacl() is the lone inconsistent path that omits the check.

Add the same num_subauth validation in set_ntacl_dacl() before copying
the ACE, matching the gate already enforced by parse_dacl().

Signed-off-by: Haofeng Li <lihaofeng@kylinos.cn>
Reviewed-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
Suggested-by: Namjae Jeon <linkinjeon@kernel.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
(cherry picked from commit 47f0b34f6bc98ed85bfdc293e8f3e432ec24958d)
Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
---
 fs/smb/server/smbacl.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/smb/server/smbacl.c b/fs/smb/server/smbacl.c
index fc9937cedb012..9c59c8f73b667 100644
--- a/fs/smb/server/smbacl.c
+++ b/fs/smb/server/smbacl.c
@@ -745,12 +745,18 @@ static void set_ntacl_dacl(struct mnt_idmap *idmap,
 			if (nt_ace_size > aces_size)
 				break;
 
+			if (ntace->sid.num_subauth == 0 ||
+			    ntace->sid.num_subauth > SID_MAX_SUB_AUTHORITIES)
+				goto next_ace;
+
 			memcpy((char *)pndace + size, ntace, nt_ace_size);
 			if (check_add_overflow(size, nt_ace_size, &size))
 				break;
+			num_aces++;
+
+next_ace:
 			aces_size -= nt_ace_size;
 			ntace = (struct smb_ace *)((char *)ntace + nt_ace_size);
-			num_aces++;
 		}
 	}
 
-- 
2.30.2

[PATCH 7.1.y 2/2] ksmbd: restore DACL size on check_add_overflow() to avoid malformed ACL

[Wentao Guan]

check_add_overflow() unconditionally writes the truncated sum into *d
even on overflow, per its contract in include/linux/overflow.h.
The four check_add_overflow() guards in set_posix_acl_entries_dacl()
and set_ntacl_dacl() break out of the ACE-building loops on overflow,
but the truncated *size is then consumed downstream at the end of
set_ntacl_dacl():

    pndacl->size = cpu_to_le16(le16_to_cpu(pndacl->size) + size);

This produces an on-wire NT ACL whose pndacl->size under-reports the
bytes actually written by the preceding fill_ace_for_sid()/memcpy()
calls, yielding a malformed ACL that can trigger out-of-bounds reads
when re-parsed by clients or ksmbd itself.

Restore *size to its pre-addition value on each overflow branch (via
`*size -= ace_sz` / `size -= nt_ace_size`) so that after the break,
*size once again holds the cumulative size of the successfully-written
ACEs. The committed ACL is then truncated-but-self-consistent rather
than malformed.

The ksmbd DACL builders are the only check_add_overflow() sites found
where an overflow path breaks out of a loop and the destination value
is consumed afterward. The other nearby break-style cases either
return -EINVAL on overflow (transport_ipc.c) or break without
consuming the overflowed destination value afterward (buildid.c).

Fixes: 299f962c0b02 ("ksmbd: use check_add_overflow() to prevent u16 DACL size overflow")
Assisted-by: atomcode:glm-5.2
Assisted-by: Codex:gpt-5.5
Cc: stable@vger.kernel.org
Signed-off-by: Wentao Guan <guanwentao@uniontech.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
---
 fs/smb/server/smbacl.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/smb/server/smbacl.c b/fs/smb/server/smbacl.c
index 9c59c8f73b667..5621c50a80571 100644
--- a/fs/smb/server/smbacl.c
+++ b/fs/smb/server/smbacl.c
@@ -649,6 +649,7 @@ static void set_posix_acl_entries_dacl(struct mnt_idmap *idmap,
 		ace_sz = fill_ace_for_sid(ntace, sid, ACCESS_ALLOWED, flags,
 				pace->e_perm, 0777);
 		if (check_add_overflow(*size, ace_sz, size)) {
+			*size -= ace_sz;
 			kfree(sid);
 			break;
 		}
@@ -663,6 +664,7 @@ static void set_posix_acl_entries_dacl(struct mnt_idmap *idmap,
 			ace_sz = fill_ace_for_sid(ntace, sid, ACCESS_ALLOWED,
 					0x03, pace->e_perm, 0777);
 			if (check_add_overflow(*size, ace_sz, size)) {
+				*size -= ace_sz;
 				kfree(sid);
 				break;
 			}
@@ -708,6 +710,7 @@ static void set_posix_acl_entries_dacl(struct mnt_idmap *idmap,
 		ace_sz = fill_ace_for_sid(ntace, sid, ACCESS_ALLOWED, 0x0b,
 				pace->e_perm, 0777);
 		if (check_add_overflow(*size, ace_sz, size)) {
+			*size -= ace_sz;
 			kfree(sid);
 			break;
 		}
@@ -750,8 +753,10 @@ static void set_ntacl_dacl(struct mnt_idmap *idmap,
 				goto next_ace;
 
 			memcpy((char *)pndace + size, ntace, nt_ace_size);
-			if (check_add_overflow(size, nt_ace_size, &size))
+			if (check_add_overflow(size, nt_ace_size, &size)) {
+				size -= nt_ace_size;
 				break;
+			}
 			num_aces++;
 
 next_ace:
-- 
2.30.2

Re: [PATCH 7.1.y 1/2] ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl

[Sasha Levin]

> [PATCH 7.1.y 1/2] ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl

I skipped this one in favour of your later v3 series, which covers 7.1 as
well and adds the other two hardening commits.  Nothing to resend here.

-- 
Thanks,
Sasha