kernel/linux.git/fs, branch v5.15.210

ksmbd: OOB read regression in smb_check_perm_dacl() ACE-walk loops

2026-06-19T11:33:51+00:00

commit 0e60dafe97eca61721f3db456f97d97a80c6c8ae upstream. Commit d07b26f39246 ("ksmbd: require minimum ACE size in smb_check_perm_dacl()") introduced a transposed bounds check: if (offsetof(struct smb_ace, sid) + aces_size < CIFS_SID_BASE_SIZE) Since offsetof(..sid) is 8 and CIFS_SID_BASE_SIZE is 8, this evaluates to `aces_size < 0`. Because `aces_size` is always non-negative, this check becomes dead code and never breaks the loop. Worse, that commit removed the old 4-byte guard, meaning the loop now reads `ace->size` (offset 2) even when `aces_size` is 0-3 bytes. This re-opens a 2-byte heap out-of-bounds (OOB) read past the pntsd allocation during subsequent SMB2_CREATE operations. Fix this by properly transposing the comparison to require at least 16 bytes (8-byte offset + 8-byte SID base), matching the correct form used in smb_inherit_dacl(). Fixes: d07b26f39246 ("ksmbd: require minimum ACE size in smb_check_perm_dacl()") Cc: stable@vger.kernel.org Signed-off-by: Ali Ganiyev Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman

nfsd: fix heap overflow in NFSv4.0 LOCK replay cache

2026-06-19T11:33:49+00:00

commit 5133b61aaf437e5f25b1b396b14242a6bb0508e2 upstream. The NFSv4.0 replay cache uses a fixed 112-byte inline buffer (rp_ibuf[NFSD4_REPLAY_ISIZE]) to store encoded operation responses. This size was calculated based on OPEN responses and does not account for LOCK denied responses, which include the conflicting lock owner as a variable-length field up to 1024 bytes (NFS4_OPAQUE_LIMIT). When a LOCK operation is denied due to a conflict with an existing lock that has a large owner, nfsd4_encode_operation() copies the full encoded response into the undersized replay buffer via read_bytes_from_xdr_buf() with no bounds check. This results in a slab-out-of-bounds write of up to 944 bytes past the end of the buffer, corrupting adjacent heap memory. This can be triggered remotely by an unauthenticated attacker with two cooperating NFSv4.0 clients: one sets a lock with a large owner string, then the other requests a conflicting lock to provoke the denial. We could fix this by increasing NFSD4_REPLAY_ISIZE to allow for a full opaque, but that would increase the size of every stateowner, when most lockowners are not that large. Instead, fix this by checking the encoded response length against NFSD4_REPLAY_ISIZE before copying into the replay buffer. If the response is too large, set rp_buflen to 0 to skip caching the replay payload. The status is still cached, and the client already received the correct response on the original request. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@kernel.org Reported-by: Nicholas Carlini Tested-by: Nicholas Carlini Signed-off-by: Jeff Layton Signed-off-by: Chuck Lever [ replaced `op_status_offset + XDR_UNIT` with existing `post_err_offset` variable ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

ksmbd: Compare MACs in constant time

2026-06-19T11:33:49+00:00

commit c5794709bc9105935dbedef8b9cf9c06f2b559fa upstream. To prevent timing attacks, MAC comparisons need to be constant-time. Replace the memcmp() with the correct function, crypto_memneq(). Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3") Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman

use less confusing names for iov_iter direction initializers

2026-06-19T11:33:46+00:00

[ Upstream commit de4eda9de2d957ef2d6a8365a01e26a435e958cb ] READ/WRITE proved to be actively confusing - the meanings are "data destination, as used with read(2)" and "data source, as used with write(2)", but people keep interpreting those as "we read data from it" and "we write data to it", i.e. exactly the wrong way. Call them ITER_DEST and ITER_SOURCE - at least that is harder to misinterpret... Signed-off-by: Al Viro Stable-dep-of: a4f0b001782b ("vsock/virtio: reset connection on receiving queue overflow") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

smb: client: require net admin for CIFS SWN netlink

2026-06-19T11:33:45+00:00

[ Upstream commit d1ebfce2c1d161186a82e77590bf7da2ea1bce91 ] CIFS_GENL_CMD_SWN_NOTIFY is the userspace witness-notify command. The intended sender is the cifs.witness helper, but the generic-netlink operation currently has no capability flag, so any local process can send RESOURCE_CHANGE or CLIENT_MOVE notifications to the in-kernel witness handler. The same family exposes CIFS_GENL_MCGRP_SWN without multicast-group capability flags. Register messages sent to that group include the witness registration id and, for NTLM-authenticated mounts, the username, domain, and password attributes copied from the CIFS session. An unprivileged local process should not be able to join that group and receive those messages. Require CAP_NET_ADMIN for incoming SWN_NOTIFY commands with GENL_ADMIN_PERM, and require CAP_NET_ADMIN over the network namespace for joining the SWN multicast group with GENL_MCAST_CAP_NET_ADMIN. The cifs.witness service runs with the privileges needed for both operations. Fixes: fed979a7e082 ("cifs: Set witness notification handler for messages from userspace daemon") Cc: stable@vger.kernel.org Signed-off-by: Michael Bommarito Assisted-by: Claude:claude-opus-4-7 Signed-off-by: Steve French Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

f2fs: fix false alarm of lockdep on cp_global_sem lock

2026-06-19T11:33:45+00:00

[ Upstream commit 6a5e3de9c2bb0b691d16789a5d19e9276a09b308 ] lockdep reported a potential deadlock: a) TCMU device removal context: - call del_gendisk() to get q->q_usage_counter - call start_flush_work() to get work_completion of wb->dwork b) f2fs writeback context: - in wb_workfn(), which holds work_completion of wb->dwork - call f2fs_balance_fs() to get sbi->gc_lock c) f2fs vfs_write context: - call f2fs_gc() to get sbi->gc_lock - call f2fs_write_checkpoint() to get sbi->cp_global_sem d) f2fs mount context: - call recover_fsync_data() to get sbi->cp_global_sem - call f2fs_check_and_fix_write_pointer() to call blkdev_report_zones() that goes down to blk_mq_alloc_request and get q->q_usage_counter Original callstack is in Closes tag. However, I think this is a false alarm due to before mount returns successfully (context d), we can not access file therein via vfs_write (context c). Let's introduce per-sb cp_global_sem_key, and assign the key for cp_global_sem, so that lockdep can recognize cp_global_sem from different super block correctly. A lot of work are done by Shin'ichiro Kawasaki, thanks a lot for the work. Fixes: c426d99127b1 ("f2fs: Check write pointer consistency of open zones") Cc: stable@kernel.org Reported-and-tested-by: Shin'ichiro Kawasaki Closes: https://lore.kernel.org/linux-f2fs-devel/20260218125237.3340441-1-shinichiro.kawasaki@wdc.com Signed-off-by: Shin'ichiro Kawasaki Signed-off-by: Chao Yu Signed-off-by: Jaegeuk Kim [ adapted to plain `struct rw_semaphore` (no `f2fs_rwsem` wrapper) and moved success-path `lockdep_unregister_key` from `kill_f2fs_super` to `f2fs_put_super` where sbi is actually freed ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

f2fs: fix incorrect file address mapping when inline inode is unwritten

2026-06-19T11:33:45+00:00

[ Upstream commit 68a0178981a0f493295afa29f8880246e561494c ] When `fileinfo->fi_flags` does not have the `FIEMAP_FLAG_SYNC` bit set and inline data has not been persisted yet, the physical address of the extent is calculated incorrectly for unwritten inline inodes. root@vm:/mnt/f2fs# dd if=/dev/zero of=data.3k bs=3k count=1 root@vm:/mnt/f2fs# f2fs_io fiemap 0 100 data.3k Fiemap: offset = 0 len = 100 logical addr. physical addr. length flags 0 0000000000000000 00000ffffffff16c 0000000000000c00 00000301 This patch fixes the issue by checking if the inode's address is valid. If the inline inode is unwritten, set the physical address to 0 and mark the extent with `FIEMAP_EXTENT_UNKNOWN | FIEMAP_EXTENT_DELALLOC` flags. Cc: stable@kernel.org Fixes: 67f8cf3cee6f ("f2fs: support fiemap for inline_data") Signed-off-by: Yongpeng Yang Reviewed-by: Chao Yu Signed-off-by: Jaegeuk Kim [ renamed `ifolio` to `ipage` in `inline_data_addr()` and `F2FS_INODE()` calls ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

smb: client: Use FullSessionKey for AES-256 encryption key derivation

2026-06-19T11:33:44+00:00

[ Upstream commit 5be7a0cef3229fb3b63a07c0d289daf752545424 ] When Kerberos authentication is used with AES-256 encryption (AES-256-CCM or AES-256-GCM), the SMB3 encryption and decryption keys must be derived using the full session key (Session.FullSessionKey) rather than just the first 16 bytes (Session.SessionKey). Per MS-SMB2 section 3.2.5.3.1, when Connection.Dialect is "3.1.1" and Connection.CipherId is AES-256-CCM or AES-256-GCM, Session.FullSessionKey must be set to the full cryptographic key from the GSS authentication context. The encryption and decryption key derivation (SMBC2SCipherKey, SMBS2CCipherKey) must use this FullSessionKey as the KDF input. The signing key derivation continues to use Session.SessionKey (first 16 bytes) in all cases. Previously, generate_key() hardcoded SMB2_NTLMV2_SESSKEY_SIZE (16) as the HMAC-SHA256 key input length for all derivations. When Kerberos with AES-256 provides a 32-byte session key, the KDF for encryption/decryption was using only the first 16 bytes, producing keys that did not match the server's, causing mount failures with sec=krb5 and require_gcm_256=1. Add a full_key_size parameter to generate_key() and pass the appropriate size from generate_smb3signingkey(): - Signing: always SMB2_NTLMV2_SESSKEY_SIZE (16 bytes) - Encryption/Decryption: ses->auth_key.len when AES-256, otherwise 16 Also fix cifs_dump_full_key() to report the actual session key length for AES-256 instead of hardcoded CIFS_SESS_KEY_SIZE, so that userspace tools like Wireshark receive the correct key for decryption. Cc: Reviewed-by: Bharath SM Signed-off-by: Piyush Sachdeva Signed-off-by: Piyush Sachdeva Signed-off-by: Steve French [ adapted to legacy crypto_shash API and ses->binding boolean instead of upstream's hmac_sha256 helpers and chan_lock machinery ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

btrfs: fix missing last_unlink_trans update when removing a directory

2026-06-19T11:33:44+00:00

[ Upstream commit 999757231c49376cd1a37308d2c8c4c9932571e1 ] When removing a directory we are not updating its last_unlink_trans field, which can result in incorrect fsync behaviour in case some one fsyncs the directory after it was removed because it's holding a file descriptor on it. Example scenario: mkdir /mnt/dir1 mkdir /mnt/dir1/dir2 mkdir /mnt/dir3 sync -f /mnt # Do some change to the directory and fsync it. chmod 700 /mnt/dir1 xfs_io -c fsync /mnt/dir1 # Move dir2 out of dir1 so that dir1 becomes empty. mv /mnt/dir1/dir2 /mnt/dir3/ open fd on /mnt/dir1 call rmdir(2) on path "/mnt/dir1" fsync fd When attempting to mount the filesystem, the log replay will fail with an -EIO error and dmesg/syslog has the following: [445771.626482] BTRFS info (device dm-0): first mount of filesystem 0368bbea-6c5e-44b5-b409-09abe496e650 [445771.626486] BTRFS info (device dm-0): using crc32c checksum algorithm [445771.627912] BTRFS info (device dm-0): start tree-log replay [445771.628335] page: refcount:2 mapcount:0 mapping:0000000061443ddc index:0x1d00 pfn:0x7072a5 [445771.629453] memcg:ffff89f400351b00 [445771.629892] aops:btree_aops [btrfs] ino:1 [445771.630737] flags: 0x17fffc00000402a(uptodate|lru|private|writeback|node=0|zone=2|lastcpupid=0x1ffff) [445771.632359] raw: 017fffc00000402a fffff47284d950c8 fffff472907b7c08 ffff89f458e412b8 [445771.633713] raw: 0000000000001d00 ffff89f6c51d1a90 00000002ffffffff ffff89f400351b00 [445771.635029] page dumped because: eb page dump [445771.635825] BTRFS critical (device dm-0): corrupt leaf: root=5 block=30408704 slot=10 ino=258, invalid nlink: has 2 expect no more than 1 for dir [445771.638088] BTRFS info (device dm-0): leaf 30408704 gen 10 total ptrs 17 free space 14878 owner 5 [445771.638091] BTRFS info (device dm-0): refs 4 lock_owner 0 current 3581087 [445771.638094] item 0 key (256 INODE_ITEM 0) itemoff 16123 itemsize 160 [445771.638097] inode generation 3 transid 9 size 16 nbytes 16384 [445771.638098] block group 0 mode 40755 links 1 uid 0 gid 0 [445771.638100] rdev 0 sequence 2 flags 0x0 [445771.638102] atime 1775744884.0 [445771.660056] ctime 1775744885.645502983 [445771.660058] mtime 1775744885.645502983 [445771.660060] otime 1775744884.0 [445771.660062] item 1 key (256 INODE_REF 256) itemoff 16111 itemsize 12 [445771.660064] index 0 name_len 2 [445771.660066] item 2 key (256 DIR_ITEM 1843588421) itemoff 16077 itemsize 34 [445771.660068] location key (259 1 0) type 2 [445771.660070] transid 9 data_len 0 name_len 4 [445771.660075] item 3 key (256 DIR_ITEM 2363071922) itemoff 16043 itemsize 34 [445771.660076] location key (257 1 0) type 2 [445771.660077] transid 9 data_len 0 name_len 4 [445771.660078] item 4 key (256 DIR_INDEX 2) itemoff 16009 itemsize 34 [445771.660079] location key (257 1 0) type 2 [445771.660080] transid 9 data_len 0 name_len 4 [445771.660081] item 5 key (256 DIR_INDEX 3) itemoff 15975 itemsize 34 [445771.660082] location key (259 1 0) type 2 [445771.660083] transid 9 data_len 0 name_len 4 [445771.660084] item 6 key (257 INODE_ITEM 0) itemoff 15815 itemsize 160 [445771.660086] inode generation 9 transid 9 size 8 nbytes 0 [445771.660087] block group 0 mode 40777 links 1 uid 0 gid 0 [445771.660088] rdev 0 sequence 2 flags 0x0 [445771.660089] atime 1775744885.641174097 [445771.660090] ctime 1775744885.645502983 [445771.660091] mtime 1775744885.645502983 [445771.660105] otime 1775744885.641174097 [445771.660106] item 7 key (257 INODE_REF 256) itemoff 15801 itemsize 14 [445771.660107] index 2 name_len 4 [445771.660108] item 8 key (257 DIR_ITEM 2676584006) itemoff 15767 itemsize 34 [445771.660109] location key (258 1 0) type 2 [445771.660110] transid 9 data_len 0 name_len 4 [445771.660111] item 9 key (257 DIR_INDEX 2) itemoff 15733 itemsize 34 [445771.660112] location key (258 1 0) type 2 [445771.660113] transid 9 data_len 0 name_len 4 [445771.660114] item 10 key (258 INODE_ITEM 0) itemoff 15573 itemsize 160 [445771.660115] inode generation 9 transid 10 size 0 nbytes 0 [445771.660116] block group 0 mode 40755 links 2 uid 0 gid 0 [445771.660117] rdev 0 sequence 0 flags 0x0 [445771.660118] atime 1775744885.645502983 [445771.660119] ctime 1775744885.645502983 [445771.660120] mtime 1775744885.645502983 [445771.660121] otime 1775744885.645502983 [445771.660122] item 11 key (258 INODE_REF 257) itemoff 15559 itemsize 14 [445771.660123] index 2 name_len 4 [445771.660124] item 12 key (258 INODE_REF 259) itemoff 15545 itemsize 14 [445771.660125] index 2 name_len 4 [445771.660126] item 13 key (259 INODE_ITEM 0) itemoff 15385 itemsize 160 [445771.660127] inode generation 9 transid 10 size 8 nbytes 0 [445771.660128] block group 0 mode 40755 links 1 uid 0 gid 0 [445771.660129] rdev 0 sequence 1 flags 0x0 [445771.660130] atime 1775744885.645502983 [445771.660130] ctime 1775744885.645502983 [445771.660131] mtime 1775744885.645502983 [445771.660132] otime 1775744885.645502983 [445771.660133] item 14 key (259 INODE_REF 256) itemoff 15371 itemsize 14 [445771.660134] index 3 name_len 4 [445771.660135] item 15 key (259 DIR_ITEM 2676584006) itemoff 15337 itemsize 34 [445771.660136] location key (258 1 0) type 2 [445771.660137] transid 10 data_len 0 name_len 4 [445771.660138] item 16 key (259 DIR_INDEX 2) itemoff 15303 itemsize 34 [445771.660139] location key (258 1 0) type 2 [445771.660140] transid 10 data_len 0 name_len 4 [445771.660144] BTRFS error (device dm-0): block=30408704 write time tree block corruption detected [445771.661650] ------------[ cut here ]------------ [445771.662358] WARNING: fs/btrfs/disk-io.c:326 at btree_csum_one_bio+0x217/0x230 [btrfs], CPU#8: mount/3581087 [445771.663588] Modules linked in: btrfs f2fs xfs (...) [445771.671229] CPU: 8 UID: 0 PID: 3581087 Comm: mount Tainted: G W 7.0.0-rc6-btrfs-next-230+ #2 PREEMPT(full) [445771.672575] Tainted: [W]=WARN [445771.672987] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014 [445771.674460] RIP: 0010:btree_csum_one_bio+0x217/0x230 [btrfs] [445771.675222] Code: 89 44 24 (...) [445771.677364] RSP: 0018:ffffd23882247660 EFLAGS: 00010246 [445771.678029] RAX: 0000000000000000 RBX: ffff89f6c51d1a90 RCX: 0000000000000000 [445771.678975] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff89f406020000 [445771.679983] RBP: ffff89f821204000 R08: 0000000000000000 R09: 00000000ffefffff [445771.680905] R10: ffffd23882247448 R11: 0000000000000003 R12: ffffd23882247668 [445771.681978] R13: ffff89f458e40fc0 R14: ffff89f737f4f500 R15: ffff89f737f4f500 [445771.682912] FS: 00007f0447a98840(0000) GS:ffff89fb9771d000(0000) knlGS:0000000000000000 [445771.684393] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [445771.685230] CR2: 00007f0447bf1330 CR3: 000000017cb02002 CR4: 0000000000370ef0 [445771.686273] Call Trace: [445771.686646] [445771.686969] btrfs_submit_bbio+0x83f/0x860 [btrfs] [445771.687750] ? write_one_eb+0x28f/0x340 [btrfs] [445771.688428] btree_writepages+0x2e3/0x550 [btrfs] [445771.689180] ? kmem_cache_alloc_noprof+0x12a/0x490 [445771.689963] ? alloc_extent_state+0x19/0x120 [btrfs] [445771.690801] ? kmem_cache_free+0x135/0x380 [445771.691328] ? preempt_count_add+0x69/0xa0 [445771.691831] ? set_extent_bit+0x252/0x8e0 [btrfs] [445771.692468] ? xas_load+0x9/0xc0 [445771.692873] ? xas_find+0x14d/0x1a0 [445771.693304] do_writepages+0xc6/0x160 [445771.693756] filemap_writeback+0xb8/0xe0 [445771.694274] btrfs_write_marked_extents+0x61/0x170 [btrfs] [445771.694999] btrfs_write_and_wait_transaction+0x4e/0xc0 [btrfs] [445771.695818] btrfs_commit_transaction+0x5c8/0xd10 [btrfs] [445771.696530] ? kmem_cache_free+0x135/0x380 [445771.697120] ? release_extent_buffer+0x34/0x160 [btrfs] [445771.697786] btrfs_recover_log_trees+0x7be/0x7e0 [btrfs] [445771.698525] ? __pfx_replay_one_buffer+0x10/0x10 [btrfs] [445771.699206] open_ctree+0x11e5/0x1810 [btrfs] [445771.699776] btrfs_get_tree.cold+0xb/0x162 [btrfs] [445771.700463] ? fscontext_read+0x165/0x180 [445771.701146] ? rw_verify_area+0x50/0x180 [445771.701866] vfs_get_tree+0x25/0xd0 [445771.702491] vfs_cmd_create+0x59/0xe0 [445771.703125] __do_sys_fsconfig+0x303/0x610 [445771.703603] do_syscall_64+0xe9/0xf20 [445771.703974] entry_SYSCALL_64_after_hwframe+0x76/0x7e [445771.704700] RIP: 0033:0x7f0447cbd4aa [445771.705108] Code: 73 01 c3 (...) [445771.707263] RSP: 002b:00007ffc4e528318 EFLAGS: 00000246 ORIG_RAX: 00000000000001af [445771.708107] RAX: ffffffffffffffda RBX: 00005561585d8c20 RCX: 00007f0447cbd4aa [445771.708931] RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000003 [445771.709744] RBP: 00005561585d9120 R08: 0000000000000000 R09: 0000000000000000 [445771.710674] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 [445771.711477] R13: 00007f0447e4f580 R14: 00007f0447e5126c R15: 00007f0447e36a23 [445771.712277] [445771.712541] ---[ end trace 0000000000000000 ]--- [445771.713382] BTRFS error (device dm-0): error while writing out transaction: -5 [445771.714679] BTRFS warning (device dm-0): Skipping commit of aborted transaction. [445771.715562] BTRFS error (device dm-0 state A): Transaction aborted (error -5) [445771.716459] BTRFS: error (device dm-0 state A) in cleanup_transaction:2068: errno=-5 IO failure [445771.717936] BTRFS error (device dm-0 state EA): failed to recover log trees with error: -5 [445771.719681] BTRFS error (device dm-0 state EA): open_ctree failed: -5 The problem is that such a fsync should have result in a fallback to a transaction commit, but that did not happen because through the btrfs_rmdir() we never update the directory's last_unlink_trans field. Any inode that had a link removed must have its last_unlink_trans updated to the ID of transaction used for the operation, otherwise fsync and log replay will not work correctly. btrfs_rmdir() calls btrfs_unlink_inode() and through that call chain we never call btrfs_record_unlink_dir() in order to update last_unlink_trans. However btrfs_unlink(), which is used for unlinking regular files, calls btrfs_record_unlink_dir() and then calls btrfs_unlink_inode(). So fix this by moving the call to btrfs_record_unlink_dir() from btrfs_unlink() to btrfs_unlink_inode(). A test case for fstests will follow soon. Reported-by: Slava0135 Link: https://lore.kernel.org/linux-btrfs/CAAJYhww5ov62Hm+n+tmhcL-e_4cBobg+OWogKjOJxVUXivC=MQ@mail.gmail.com/ CC: stable@vger.kernel.org Signed-off-by: Filipe Manana Signed-off-by: David Sterba [ wrapped dir and inode arguments with BTRFS_I() since 6.1 btrfs_rmdir() uses struct inode * instead of struct btrfs_inode * ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

smb: client: validate dacloffset before building DACL pointers

2026-06-19T11:33:44+00:00

[ Upstream commit f98b48151cc502ada59d9778f0112d21f2586ca3 ] parse_sec_desc(), build_sec_desc(), and the chown path in id_mode_to_cifs_acl() all add the server-supplied dacloffset to pntsd before proving a DACL header fits inside the returned security descriptor. On 32-bit builds a malicious server can return dacloffset near U32_MAX, wrap the derived DACL pointer below end_of_acl, and then slip past the later pointer-based bounds checks. build_sec_desc() and id_mode_to_cifs_acl() can then dereference DACL fields from the wrapped pointer in the chmod/chown rewrite paths. Validate dacloffset numerically before building any DACL pointer and reuse the same helper at the three DACL entry points. Fixes: bc3e9dd9d104 ("cifs: Change SIDs in ACEs while transferring file ownership.") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-6 Signed-off-by: Michael Bommarito Signed-off-by: Steve French [ renamed smb_ntsd/smb_acl structs to cifs_ntsd/cifs_acl and kept existing inline ACL size check instead of using missing validate_dacl() helper ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman