From: Pavel Paklov pavel.paklov@cyberprotect.ru
From: Paulo Alcantara pc@manguebit.com
commit fa2f9906a7b333ba757a7dbae0713d8a5396186e upstream
When shutting down the server in cifs_put_tcp_session(), cifsd thread might be reconnecting to multiple DFS targets before it realizes it should exit the loop, so @server->hostname can't be freed as long as cifsd thread isn't done. Otherwise the following can happen:
RIP: 0010:__slab_free+0x223/0x3c0 Code: 5e 41 5f c3 cc cc cc cc 4c 89 de 4c 89 cf 44 89 44 24 08 4c 89 1c 24 e8 fb cf 8e 00 44 8b 44 24 08 4c 8b 1c 24 e9 5f fe ff ff <0f> 0b 41 f7 45 08 00 0d 21 00 0f 85 2d ff ff ff e9 1f ff ff ff 80 RSP: 0018:ffffb26180dbfd08 EFLAGS: 00010246 RAX: ffff8ea34728e510 RBX: ffff8ea34728e500 RCX: 0000000000800068 RDX: 0000000000800068 RSI: 0000000000000000 RDI: ffff8ea340042400 RBP: ffffe112041ca380 R08: 0000000000000001 R09: 0000000000000000 R10: 6170732e31303000 R11: 70726f632e786563 R12: ffff8ea34728e500 R13: ffff8ea340042400 R14: ffff8ea34728e500 R15: 0000000000800068 FS: 0000000000000000(0000) GS:ffff8ea66fd80000(0000) 000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffc25376080 CR3: 000000012a2ba001 CR4: PKRU: 55555554 Call Trace: <TASK> ? show_trace_log_lvl+0x1c4/0x2df ? show_trace_log_lvl+0x1c4/0x2df ? __reconnect_target_unlocked+0x3e/0x160 [cifs] ? __die_body.cold+0x8/0xd ? die+0x2b/0x50 ? do_trap+0xce/0x120 ? __slab_free+0x223/0x3c0 ? do_error_trap+0x65/0x80 ? __slab_free+0x223/0x3c0 ? exc_invalid_op+0x4e/0x70 ? __slab_free+0x223/0x3c0 ? asm_exc_invalid_op+0x16/0x20 ? __slab_free+0x223/0x3c0 ? extract_hostname+0x5c/0xa0 [cifs] ? extract_hostname+0x5c/0xa0 [cifs] ? __kmalloc+0x4b/0x140 __reconnect_target_unlocked+0x3e/0x160 [cifs] reconnect_dfs_server+0x145/0x430 [cifs] cifs_handle_standard+0x1ad/0x1d0 [cifs] cifs_demultiplex_thread+0x592/0x730 [cifs] ? __pfx_cifs_demultiplex_thread+0x10/0x10 [cifs] kthread+0xdd/0x100 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x29/0x50 </TASK>
Fixes: 7be3248f3139 ("cifs: To match file servers, make sure the server hostname matches") Reported-by: Jay Shin jaeshin@redhat.com Signed-off-by: Paulo Alcantara (Red Hat) pc@manguebit.com Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Pavel Paklov pavel.paklov@cyberprotect.ru --- Backport fix for CVE-2025-21673 fs/smb/client/connect.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c index 01ce81f77e89..2b0657fe2a3f 100644 --- a/fs/smb/client/connect.c +++ b/fs/smb/client/connect.c @@ -1066,6 +1066,7 @@ static void clean_demultiplex_info(struct TCP_Server_Info *server) kfree(server->origin_fullpath); kfree(server->leaf_fullpath); #endif + kfree(server->hostname); kfree(server);
length = atomic_dec_return(&tcpSesAllocCount); @@ -1688,8 +1689,6 @@ cifs_put_tcp_session(struct TCP_Server_Info *server, int from_reconnect) kfree_sensitive(server->session_key.response); server->session_key.response = NULL; server->session_key.len = 0; - kfree(server->hostname); - server->hostname = NULL;
task = xchg(&server->tsk, NULL); if (task)