TLDRVuln - Cybersecurity Vulnerabilities Made Simple

In the Linux kernel, the following vulnerability has been resolved:

smb: client: fix double free of TCP_Server_Info::hostname

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

? __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]

? __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>