kernel/git/stable/linux.git/fs/smb/client, branch master

Merge tag 'cifs-fixes-7.3-rc3' of https://git.manguebit.org/linux

2026-09-10T21:03:48+00:00

Pull smb client fixes from Paulo Alcantara: - File type corruption fixes in reparse point handling: setting S_IFMT bits without clearing the existing type first corrupted the file mode (e.g. S_IFREG | S_IFCHR == S_IFLNK). Fixed in the WSL, POSIX and native symlink reparse parsers. Also fixes an uninitialized SID structure in the POSIX readdir path when parsing fails. - Ownership mapping fixes: forceuid/forcegid mount options were ignored in several code paths (SID-to-id mapping, WSL extended attributes, POSIX extensions getattr), allowing an untrusted server to dictate local file ownership despite explicit mount overrides. - Heap overflow and overflow fixes in DACL rewriting: replacing short SIDs with long ones could overflow the DACL buffer, and the u16 accumulator for DACL size could wrap around with enough ACEs. - Reference count leak fixes in oplock break and deferred close: duplicate oplock breaks on a queued work item leaked a cifsFileInfo reference, and deferred close had a similar leak when requeueing a running work item. Both cause busy-inode oopses on unmount. - DFS superblock use-after-free fix: the iterator callback stored a raw superblock pointer without pinning it, racing with automount expiry. - One-byte slab OOB read in the native symlink parser when handling share-root relative paths. - Hardening of legacy SMB1 input: reject userspace-crafted cifs.idmap key descriptions that bypass kernel origin checks, and validate DataOffset in CIFSSMBRead() to prevent heap info disclosure from a malicious server. - DFS cache fix: defer metadata updates until target copying succeeds to prevent partial-state cache entries on allocation failure. * tag 'cifs-fixes-7.3-rc3' of https://git.manguebit.org/linux: smb: client: fix one-byte OOB read in smb2_parse_native_symlink() smb: client: fail DACL rewrite when the new DACL exceeds 64K smb: client: fix heap overflow in DACL owner/group rewrite smb: client: fix file type corruption in cifs_reparse_point_to_fattr() smb: client: fix file type corruption in posix_reparse_to_fattr() smb: client: fix file type corruption in wsl_to_fattr() smb: client: avoid using uninitialized SIDs in cifs_posix_to_fattr() smb: client: fix WSL reparse point uid/gid override smb: client: honor forceuid/forcegid when mapping SIDs to uid/gid smb: client: fix uid/gid override in getattr with posix extensions smb: client: fix cifsFileInfo reference leak in deferred close smb: client: avoid leaking refcount when cifs_sb_tlink() fails smb: client: avoid leaking refcount in cifs_queue_oplock_break() smb: client: fill cache fields after populating cache in copy_ref_data() smb: client: pin DFS superblock in iterator callback smb: client: reject userspace cifs.idmap descriptions smb: client: reject out-of-bounds DataOffset in CIFSSMBRead() smb: client: reject short READ responses in CIFSSMBRead()

smb: client: fix one-byte OOB read in smb2_parse_native_symlink()

2026-09-10T01:06:05+00:00

When parsing a share-root relative native symlink, memcpy copies smb_target+1 (skipping the leading separator) but uses strlen(smb_target)+1 as the length, reading one byte past the allocated buffer. This fixes the following KASAN splat when accessing an SMB symlink with a target of '\a\b': BUG: KASAN: slab-out-of-bounds in smb2_parse_native_symlink+0x4f5/0xca0 Read of size 5 at addr ffff88800878fe21 by task netfsfuzz-execu/1 CPU: 1 UID: 0 PID: 1 Comm: netfsfuzz-execu Tainted: G N 7.2.0-11943-g2709dd5ae32f-dirty #1 PREEMPT(lazy) Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996) Call Trace: dump_stack_lvl+0x7b/0xa0 print_report+0xd0/0x630 kasan_report+0xe5/0x120 kasan_check_range+0x105/0x1b0 __asan_memcpy+0x23/0x60 smb2_parse_native_symlink+0x4f5/0xca0 parse_reparse_point+0x68a/0x1530 reparse_info_to_fattr+0x752/0xa20 cifs_get_fattr+0x873/0x15b0 cifs_get_inode_info+0xc0/0x310 cifs_lookup+0x308/0xa70 __lookup_slow+0x122/0x2b0 lookup_slow+0x50/0x70 path_lookupat+0x525/0xaf0 filename_lookup+0x1f2/0x550 vfs_statx+0xd1/0x1a0 vfs_fstatat+0x65/0xc0 __do_sys_newfstatat+0x9a/0x120 do_syscall_64+0xdd/0x4a0 entry_SYSCALL_64_after_hwframe+0x77/0x7f Reported-by: Yuanfu Xie Fixes: 723f4ef90452 ("cifs: Fix parsing native symlinks relative to the export") Suggested-by: Pali Rohar Reviewed-by: Pali Rohar Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: stable@vger.kernel.org

smb: client: fail DACL rewrite when the new DACL exceeds 64K

2026-09-09T14:56:47+00:00

replace_sids_and_copy_aces() and set_chmod_dacl() accumulate the size of the DACL they build in a u16. That accumulator can wrap. validate_dacl() caps num_aces at (dacl_size - sizeof(struct smb_acl)) / 20, i.e. 3276 for a maximally sized DACL, while each rewritten ACE can grow to sizeof(struct smb_ace) (76 bytes) once its SID is replaced with one carrying SID_MAX_SUB_AUTHORITIES sub-authorities. The worst case is therefore sizeof(struct smb_acl) + 3276 * 76 = 248984 bytes, far beyond what a u16 can hold. A wraparound is reached with 863 ACEs. After the wraparound, ndacl_ptr->size becomes meaningless and the offset will point anywhere in the ACE array. As a result, we will see corruption of the DACL, which then gets sent to the server. This is not an out-of-bounds write as the allocation now covers the worst-case expansion, so writes will always go into the buffer. Adjust the code to use a u32 internally and return -EOVERFLOW in the overflow case. The operation must be refused, because a DACL can only hold 2^16-1 bytes on the wire and larger DACLs cannot be represented. set_chmod_dacl() carries the same pattern and is fixed the same way. It only wraps once the source DACL comes within roughly 380 bytes of the 64K ceiling, but the failure mode is identical. Suggested-by: Namjae Jeon Cc: stable@vger.kernel.org Fixes: f5065508897a ("cifs: Retain old ACEs when converting between mode bits and ACL.") Assisted-by: Kiro:claude-opus-5 Signed-off-by: Bjoern Doebel Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara

smb: client: fix heap overflow in DACL owner/group rewrite

2026-09-09T14:56:47+00:00

When id_mode_to_cifs_acl rewrites an existing DACL, it allocates a buffer sized according to the on-disk DACL length reported by dacl_ptr->size. However, replace_sids_and_copy_aces may rewrite each ACE with a new owner/group SID obtained from the cifs.idmap upcall. Those SIDs can have up to SID_MAX_SUB_AUTHORITIES (15) sub-authorities, making each ACE up to 76 bytes (sizeof(struct smb_ace)). If the original DACL contains short SIDs (e.g., 1 sub-authority) while the replacement SIDs are long, the rewritten ACEs overflow the allocation. Fix this by always budgeting for worst-case SID expansion: allocate sizeof(struct smb_acl) plus num_aces * sizeof(struct smb_ace), which covers the smb_acl header and room for every ACE at maximum SID size. This replaces the previous split logic that used dacl_ptr->size for cifsacl mounts but num_aces * sizeof(struct smb_ace) for mode_from_sid mounts: both paths can trigger the same rewrite and need the same headroom. KASAN reports this as: BUG: KASAN: slab-out-of-bounds in build_sec_desc+0x1e8a/0x2680 [cifs] Write of size 4 at addr ffff8881a5e25374 by task chown/5298 ... The buggy address is located 0 bytes to the right of allocated 884-byte region [ffff8881a5e25000, ffff8881a5e25374) Cc: stable@vger.kernel.org Fixes: bc3e9dd9d104 ("cifs: Change SIDs in ACEs while transferring file ownership.") Assisted-by: Kiro:claude-opus-4.6 Signed-off-by: Bjoern Doebel Reviewed-by: Namjae Jeon Fixes: 5c3564852c58 ("cifs: Minimize the number of cifs_acl memory allocations") Signed-off-by: Paulo Alcantara

smb: client: fix file type corruption in cifs_reparse_point_to_fattr()

2026-09-08T14:30:27+00:00

Setting the file type in cf_mode without clearing the existing S_IFMT bits first is wrong as it corrupts the file type when cf_mode already has type bits set (e.g. S_IFREG | S_IFLNK == S_IFDIR | S_IFREG). Clear S_IFMT before setting S_IFLNK for native and SMB1 symlinks. Closes: https://sashiko.dev/#/patchset/20260906181540.647469-1-pc%40manguebit.org Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: stable@vger.kernel.org

smb: client: fix file type corruption in posix_reparse_to_fattr()

2026-09-08T14:30:18+00:00

Setting the file type in cf_mode without clearing the existing S_IFMT bits first is wrong as it corrupts the file type when cf_mode already has type bits set (e.g. S_IFREG | S_IFCHR == S_IFLNK). Use a local ftype variable to collect the new file type and apply it after validation succeeds, clearing S_IFMT and setting the new type in a single assignment. This avoids stripping cf_mode on malformed reparse points where the function returns false early. Closes: https://sashiko.dev/#/patchset/20260906172005.627163-1-pc%40manguebit.org Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: stable@vger.kernel.org

smb: client: fix file type corruption in wsl_to_fattr()

2026-09-08T14:30:08+00:00

Setting the file type in cf_mode without clearing the existing S_IFMT bits first is wrong as it corrupts the file type when cf_mode already has type bits set (e.g. S_IFREG | S_IFCHR == S_IFLNK). Clear S_IFMT before the switch statement. Closes: https://sashiko.dev/#/patchset/20260906172005.627163-1-pc%40manguebit.org Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: stable@vger.kernel.org

smb: client: avoid using uninitialized SIDs in cifs_posix_to_fattr()

2026-09-08T14:29:57+00:00

cifs_posix_to_fattr() ignores the return value of posix_info_parse(). When a malformed POSIX directory entry is encountered (e.g. invalid SID lengths from an untrusted server), posix_info_parse() returns -1 without populating the 'parsed' struct. The uninitialized stack memory in parsed.owner and parsed.group is then passed to sid_to_id(), which processes the garbage bytes and passes them to request_key() to construct a SID string, potentially leaking kernel stack contents to the userspace idmap daemon. Fix this by checking the return value and skipping the SID-to-id mapping when parsing fails. The remaining fattr fields (timestamps, mode, etc.) are populated directly from the 'info' pointer so they are unaffected. Closes: https://sashiko.dev/#/patchset/20260906172005.627163-1-pc%40manguebit.org Closes: https://sashiko.dev/#/patchset/20260906181540.647469-1-pc%40manguebit.org Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: stable@vger.kernel.org

smb: client: fix WSL reparse point uid/gid override

2026-09-08T14:29:44+00:00

wsl_to_fattr() unconditionally overwrites cf_uid/cf_gid with values from WSL extended attributes ($LXUID/$LXGID), ignoring the forceuid and forcegid mount options. Fix this by initializing cf_uid/cf_gid to the mount defaults and gating the $LXUID/$LXGID EA parsing on forceuid/forcegid. Closes: https://sashiko.dev/#/patchset/20260906190803.667489-1-pc%40manguebit.org Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: stable@vger.kernel.org

smb: client: honor forceuid/forcegid when mapping SIDs to uid/gid

2026-09-08T14:29:31+00:00

When the administrator mounts with forceuid or forcegid (uid=/gid= mount options), they expect all files to appear owned by the specified user/group. However, several code paths unconditionally called sid_to_id() to overwrite cf_uid/cf_gid with server-provided values, ignoring the administrator's explicit override: - smb311_posix_info_to_fattr() (stat via POSIX extensions) - cifs_posix_to_fattr() (readdir via POSIX extensions) - parse_sec_desc() (CIFS ACL ownership mapping) This allowed an untrusted server to dictate local file ownership even when the mount was configured to force specific uid/gid values. Fix all three call sites to check CIFS_MOUNT_OVERR_UID and CIFS_MOUNT_OVERR_GID before calling sid_to_id(), following the same pattern already used by cifs_unix_basic_to_fattr() for unix extensions. Closes: https://sashiko.dev/#/patchset/20260906155816.603278-1-pc%40manguebit.org Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: stable@vger.kernel.org