Introduce smb_validate_ntsd_sid() helper to safely validate Owner SID
and Group SID inside the NT Security Descriptor (smb_ntsd) retrieved
from the parent directory.
Cc: stable@vger.kernel.org
Signed-off-by: Junyi Liu <moss80199@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Commit 299f962c0b ("ksmbd: use check_add_overflow() to prevent u16
DACL size overflow") added check_add_overflow() guards that break out
of the ACE-building loops in set_posix_acl_entries_dacl() when the
accumulated DACL size would wrap past 65535.
However, each iteration allocates a struct smb_sid via kmalloc_obj()
at the top of the loop and relies on the kfree(sid) call at the end
of the loop body (the 'pass_same_sid' label in the first loop, and
the explicit kfree at the tail of the second loop) to release it.
The newly introduced 'break' statements bypass those kfree() calls,
leaking the sid buffer every time an overflow is detected.
A malicious or malformed file with enough POSIX ACL entries to trip
the overflow check will leak one or more struct smb_sid allocations
on every request that touches the file's DACL, providing a trivial
kernel memory exhaustion vector.
Free sid before breaking out of the loops to plug the leak.
Fixes: 299f962c0b ("ksmbd: use check_add_overflow() to prevent u16 DACL size overflow")
Cc: stable@vger.kernel.org
Signed-off-by: Ferry Meng <mengferry@linux.alibaba.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
smb_inherit_dacl() walks the parent directory DACL loaded from the
security descriptor xattr. It verifies that each ACE contains the fixed
SID header before using it, but does not verify that the variable-length
SID described by sid.num_subauth is fully contained in the ACE.
A malformed inheritable ACE can advertise more subauthorities than are
present in the ACE. compare_sids() may then read past the ACE.
smb_set_ace() also clamps the copied destination SID, but used the
unchecked source SID count to compute the inherited ACE size. That could
advance the temporary inherited ACE buffer pointer and nt_size accounting
past the allocated buffer.
Fix this by validating the parent ACE SID count and SID length before
using the SID during inheritance. Compute the inherited ACE size from the
copied SID so the size matches the bounded destination SID. Reject the
inherited DACL if size accumulation would overflow smb_acl.size or the
security descriptor allocation size.
Fixes: e2f34481b2 ("cifsd: add server-side procedures for SMB3")
Signed-off-by: Shota Zaizen <s@zaizen.me>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
set_posix_acl_entries_dacl() and set_ntacl_dacl() accumulate ACE sizes
in u16 variables. When a file has many POSIX ACL entries, the
accumulated size can wrap past 65535, causing the pointer arithmetic
(char *)pndace + *size to land within already-written ACEs. Subsequent
writes then overwrite earlier entries, and pndacl->size gets a
truncated value.
Use check_add_overflow() at each accumulation point to detect the
wrap before it corrupts the buffer, consistent with existing
check_mul_overflow() usage elsewhere in smbacl.c.
Cc: stable@vger.kernel.org
Fixes: e2f34481b2 ("cifsd: add server-side procedures for SMB3")
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
smb_inherit_dacl() trusts the on-disk num_aces value from the parent
directory's DACL xattr and uses it to size a heap allocation:
aces_base = kmalloc(sizeof(struct smb_ace) * num_aces * 2, ...);
num_aces is a u16 read from le16_to_cpu(parent_pdacl->num_aces)
without checking that it is consistent with the declared pdacl_size.
An authenticated client whose parent directory's security.NTACL is
tampered (e.g. via offline xattr corruption or a concurrent path that
bypasses parse_dacl()) can present num_aces = 65535 with minimal
actual ACE data. This causes a ~8 MB allocation (not kzalloc, so
uninitialized) that the subsequent loop only partially populates, and
may also overflow the three-way size_t multiply on 32-bit kernels.
Additionally, the ACE walk loop uses the weaker
offsetof(struct smb_ace, access_req) minimum size check rather than
the minimum valid on-wire ACE size, and does not reject ACEs whose
declared size is below the minimum.
Reproduced on UML + KASAN + LOCKDEP against the real ksmbd code path.
A legitimate mount.cifs client creates a parent directory over SMB
(ksmbd writes a valid security.NTACL xattr), then the NTACL blob on
the backing filesystem is rewritten to set num_aces = 0xFFFF while
keeping the posix_acl_hash bytes intact so ksmbd_vfs_get_sd_xattr()'s
hash check still passes. A subsequent SMB2 CREATE of a child under
that parent drives smb2_open() into smb_inherit_dacl() (share has
"vfs objects = acl_xattr" set), which fails the page allocator:
WARNING: mm/page_alloc.c:5226 at __alloc_frozen_pages_noprof+0x46c/0x9c0
Workqueue: ksmbd-io handle_ksmbd_work
__alloc_frozen_pages_noprof+0x46c/0x9c0
___kmalloc_large_node+0x68/0x130
__kmalloc_large_node_noprof+0x24/0x70
__kmalloc_noprof+0x4c9/0x690
smb_inherit_dacl+0x394/0x2430
smb2_open+0x595d/0xabe0
handle_ksmbd_work+0x3d3/0x1140
With the patch applied the added guard rejects the tampered value
with -EINVAL before any large allocation runs, smb2_open() falls back
to smb2_create_sd_buffer(), and the child is created with a default
SD. No warning, no splat.
Fix by:
1. Validating num_aces against pdacl_size using the same formula
applied in parse_dacl().
2. Replacing the raw kmalloc(sizeof * num_aces * 2) with
kmalloc_array(num_aces * 2, sizeof(...)) for overflow-safe
allocation.
3. Tightening the per-ACE loop guard to require the minimum valid
ACE size (offsetof(smb_ace, sid) + CIFS_SID_BASE_SIZE) and
rejecting under-sized ACEs, matching the hardening in
smb_check_perm_dacl() and parse_dacl().
v1 -> v2:
- Replace the synthetic test-module splat in the changelog with a
real-path UML + KASAN reproduction driven through mount.cifs and
SMB2 CREATE; Namjae flagged the kcifs3_test_inherit_dacl_old name
in v1 since it does not exist in ksmbd.
- Drop the commit-hash citation from the code comment per Namjae's
review; keep the parse_dacl() pointer.
Fixes: e2f34481b2 ("cifsd: add server-side procedures for SMB3")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Both ACE-walk loops in smb_check_perm_dacl() only guard against an
under-sized remaining buffer, not against an ACE whose declared
`ace->size` is smaller than the struct it claims to describe:
if (offsetof(struct smb_ace, access_req) > aces_size)
break;
ace_size = le16_to_cpu(ace->size);
if (ace_size > aces_size)
break;
The first check only requires the 4-byte ACE header to be in bounds;
it does not require access_req (4 bytes at offset 4) to be readable.
An attacker who has set a crafted DACL on a file they own can declare
ace->size == 4 with aces_size == 4, pass both checks, and then
granted |= le32_to_cpu(ace->access_req); /* upper loop */
compare_sids(&sid, &ace->sid); /* lower loop */
reads access_req at offset 4 (OOB by up to 4 bytes) and ace->sid at
offset 8 (OOB by up to CIFS_SID_BASE_SIZE + SID_MAX_SUB_AUTHORITIES
* 4 bytes).
Tighten both loops to require
ace_size >= offsetof(struct smb_ace, sid) + CIFS_SID_BASE_SIZE
which is the smallest valid on-wire ACE layout (4-byte header +
4-byte access_req + 8-byte sid base with zero sub-auths). Also
reject ACEs whose sid.num_subauth exceeds SID_MAX_SUB_AUTHORITIES
before letting compare_sids() dereference sub_auth[] entries.
parse_sec_desc() already enforces an equivalent check (lines 441-448);
smb_check_perm_dacl() simply grew weaker validation over time.
Reachability: authenticated SMB client with permission to set an ACL
on a file. On a subsequent CREATE against that file, the kernel
walks the stored DACL via smb_check_perm_dacl() and triggers the
OOB read. Not pre-auth, and the OOB read is not reflected to the
attacker, but KASAN reports and kernel state corruption are
possible.
Fixes: e2f34481b2 ("cifsd: add server-side procedures for SMB3")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-6
Assisted-by: Codex:gpt-5-4
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
parse_dacl() compares each ACE SID against sid_unix_NFS_mode and on
match reads sid.sub_auth[2] as the file mode. If sid_unix_NFS_mode is
the prefix S-1-5-88-3 with num_subauth = 2 then compare_sids() compares
only min(num_subauth, 2) sub-authorities so a client SID with
num_subauth = 2 and sub_auth = {88, 3} will match.
If num_subauth = 2 and the ACE is placed at the very end of the security
descriptor, sub_auth[2] will be 4 bytes past end_of_acl. The
out-of-band bytes will then be masked to the low 9 bits and applied as
the file's POSIX mode, probably not something that is good to have
happen.
Fix this up by forcing the SID to actually carry a third sub-authority
before reading it at all.
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Steve French <smfrench@gmail.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Tom Talpey <tom@talpey.com>
Cc: linux-cifs@vger.kernel.org
Cc: <stable@kernel.org>
Assisted-by: gregkh_clanker_t1000
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
When a compound request such as READ + QUERY_INFO(Security) is received,
and the first command (READ) consumes most of the response buffer,
ksmbd could write beyond the allocated buffer while building a security
descriptor.
The root cause was that smb2_get_info_sec() checked buffer space using
ppntsd_size from xattr, while build_sec_desc() often synthesized a
significantly larger descriptor from POSIX ACLs.
This patch introduces smb_acl_sec_desc_scratch_len() to accurately
compute the final descriptor size beforehand, performs proper buffer
checking with smb2_calc_max_out_buf_len(), and uses exact-sized
allocation + iov pinning.
Cc: stable@vger.kernel.org
Fixes: e2b76ab8b5 ("ksmbd: add support for read compound")
Signed-off-by: Asim Viladi Oglu Manizada <manizada@pm.me>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:
Single allocations: kmalloc(sizeof(TYPE), ...)
are replaced with: kmalloc_obj(TYPE, ...)
Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with: kmalloc_objs(TYPE, COUNT, ...)
Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...)
(where TYPE may also be *VAR)
The resulting allocations no longer return "void *", instead returning
"TYPE *".
Signed-off-by: Kees Cook <kees@kernel.org>
A zero value of pdacl->num_aces is already handled at the start of
smb_check_perm_dacl() so the second check is useless.
Drop the unreachable code block, no functional impact intended.
Found by Linux Verification Center (linuxtesting.org) with SVACE.
Signed-off-by: Alexey Velichayshiy <a.velichayshiy@ispras.ru>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Access psid->sub_auth[psid->num_subauth - 1] without checking
if num_subauth is non-zero leads to an out-of-bounds read.
This patch adds a validation step to ensure num_subauth != 0
before sub_auth is accessed.
Cc: stable@vger.kernel.org
Signed-off-by: Norbert Szetei <norbert@doyensec.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
The dacloffset field was originally typed as int and used in an
unchecked addition, which could overflow and bypass the existing
bounds check in both smb_check_perm_dacl() and smb_inherit_dacl().
This could result in out-of-bounds memory access and a kernel crash
when dereferencing the DACL pointer.
This patch converts dacloffset to unsigned int and uses
check_add_overflow() to validate access to the DACL.
Cc: stable@vger.kernel.org
Signed-off-by: Norbert Szetei <norbert@doyensec.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
parse_dcal() validate num_aces to allocate posix_ace_state_array.
if (num_aces > ULONG_MAX / sizeof(struct smb_ace *))
It is an incorrect validation that we can create an array of size ULONG_MAX.
smb_acl has ->size field to calculate actual number of aces in request buffer
size. Use this to check invalid num_aces.
Reported-by: Igor Leite Ladessa <igor-ladessa@hotmail.com>
Tested-by: Igor Leite Ladessa <igor-ladessa@hotmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
2.4.5 in [MS-DTYP].pdf describe the data type of num_aces as le16.
AceCount (2 bytes): An unsigned 16-bit integer that specifies the count
of the number of ACE records in the ACL.
Change it to le16 and add reserved field to smb_acl struct.
Reported-by: Igor Leite Ladessa <igor-ladessa@hotmail.com>
Tested-by: Igor Leite Ladessa <igor-ladessa@hotmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
If osidoffset, gsidoffset and dacloffset could be greater than smb_ntsd
struct size. If it is smaller, It could cause slab-out-of-bounds.
And when validating sid, It need to check it included subauth array size.
Cc: stable@vger.kernel.org
Reported-by: Norbert Szetei <norbert@doyensec.com>
Tested-by: Norbert Szetei <norbert@doyensec.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Prefer to report ENOMEM rather than incur the oom for allocations in
ksmbd. __GFP_NORETRY could not achieve that, It would fail the allocations
just too easily. __GFP_RETRY_MAYFAIL will keep retrying the allocation
until there is no more progress and fail the allocation instead go OOM
and let the caller to deal with it.
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
The ppace array is not freed if one of the init_acl_state() calls inside
parse_dacl() fails. At the moment the function may fail only due to the
memory allocation errors so it's highly unlikely in this case but
nevertheless a fix is needed.
Move ppace allocation after the init_acl_state() calls with proper error
handling.
Found by Linux Verification Center (linuxtesting.org).
Fixes: e2f34481b2 ("cifsd: add server-side procedures for SMB3")
Cc: stable@vger.kernel.org
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
slab out-of-bounds write is caused by that offsets is bigger than pntsd
allocation size. This patch add the check to validate 3 offsets using
allocation size.
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-22271
Cc: stable@vger.kernel.org
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
mark_inode_dirty will be called in notify_change().
This patch remove unneeded mark_inode_dirty in set_info_sec().
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
It would be better to replace the traditional ternary conditional
operator with min() in compare_sids.
Signed-off-by: Lu Hongfei <luhongfei@vivo.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
ksmbd is doing write access using vfs helpers. There are the cases that
mnt_want_write() is not called in vfs helper. This patch add missing
mnt_want_write() to ksmbd vfs functions.
Cc: stable@vger.kernel.org
Cc: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Dan reported the following error message:
fs/smb/server/smbacl.c:1296 smb_check_perm_dacl()
error: 'posix_acls' dereferencing possible ERR_PTR()
fs/smb/server/vfs.c:1323 ksmbd_vfs_make_xattr_posix_acl()
error: 'posix_acls' dereferencing possible ERR_PTR()
fs/smb/server/vfs.c:1830 ksmbd_vfs_inherit_posix_acl()
error: 'acls' dereferencing possible ERR_PTR()
__get_acl() returns a mix of error pointers and NULL. This change it
with IS_ERR_OR_NULL().
Fixes: e2f34481b2 ("cifsd: add server-side procedures for SMB3")
Cc: stable@vger.kernel.org
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Move CIFS/SMB3 related client and server files (cifs.ko and ksmbd.ko
and helper modules) to new fs/smb subdirectory:
fs/cifs --> fs/smb/client
fs/ksmbd --> fs/smb/server
fs/smbfs_common --> fs/smb/common
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
