smb: client: fix use-after-free bug in cifs_debug_data_proc_show()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix use-after-free bug in cifs_debug_data_proc_show() Skip SMB sessions that are being teared down (e.g. @ses->ses_status == SES_EXITING) in cifs_debug_data_proc_show() to avoid use-after-free in @ses. This fixes the following GPF when reading from /proc/fs/cifs/DebugData while mounting and umounting [ 816.251274] general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6d81: 0000 [#1] PREEMPT SMP NOPTI ... [ 816.260138] Call Trace: [ 816.260329] <TASK> [ 816.260499] ? die_addr+0x36/0x90 [ 816.260762] ? exc_general_protection+0x1b3/0x410 [ 816.261126] ? asm_exc_general_protection+0x26/0x30 [ 816.261502] ? cifs_debug_tcon+0xbd/0x240 [cifs] [ 816.261878] ? cifs_debug_tcon+0xab/0x240 [cifs] [ 816.262249] cifs_debug_data_proc_show+0x516/0xdb0 [cifs] [ 816.262689] ? seq_read_iter+0x379/0x470 [ 816.262995] seq_read_iter+0x118/0x470 [ 816.263291] proc_reg_read_iter+0x53/0x90 [ 816.263596] ? srso_alias_return_thunk+0x5/0x7f [ 816.263945] vfs_read+0x201/0x350 [ 816.264211] ksys_read+0x75/0x100 [ 816.264472] do_syscall_64+0x3f/0x90 [ 816.264750] entry_SYSCALL_64_after_hwframe+0x6e/0xd8 [ 816.265135] RIP: 0033:0x7fd5e669d381

References

• https://git.kernel.org/stable/c/2abdf136784b7edaec7ffe0f4b461b63f9c4c4de
• https://git.kernel.org/stable/c/336a066990bb3962c46daf574ace596bda9303ce
• https://git.kernel.org/stable/c/558817597d5fbd7af31f891b67b0fd20f0d047b7
• https://git.kernel.org/stable/c/89929ea46f9cc11ba66d2c64713aa5d5dc723b09
• https://git.kernel.org/stable/c/0ab6f842452ce2cae04209d4671ac6289d0aef8a
• https://git.kernel.org/stable/c/d328c09ee9f15ee5a26431f5aad7c9239fa85e62