From: Paulo Alcantara pc@manguebit.com

commit d328c09ee9f15ee5a26431f5aad7c9239fa85e62 upstream.

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+0x36/0x90м [ 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

Cc: stable@vger.kernel.org Signed-off-by: Paulo Alcantara (SUSE) pc@manguebit.com Signed-off-by: Steve French stfrench@microsoft.com [d.privalov: Adapt checking status ses->ses_status to use global lock GlobalMid_Lock] Signed-off-by: Dmitriy Privalov d.privalov@omp.ru --- fs/cifs/cifs_debug.c | 6 ++++++ 1 file changed, 6 insertions(+)

diff --git a/fs/cifs/cifs_debug.c b/fs/cifs/cifs_debug.c index 53588d7517b4..c094f44fbbde 100644 --- a/fs/cifs/cifs_debug.c +++ b/fs/cifs/cifs_debug.c @@ -356,6 +356,11 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v) list_for_each(tmp2, &server->smb_ses_list) { ses = list_entry(tmp2, struct cifs_ses, smb_ses_list); + spin_lock(&GlobalMid_Lock); + if (ses->status == CifsExiting) { + spin_unlock(&GlobalMid_Lock); + continue; + } if ((ses->serverDomain == NULL) || (ses->serverOS == NULL) || (ses->serverNOS == NULL)) { @@ -375,6 +380,7 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v) ses->capabilities, ses->status); } + spin_unlock(&GlobalMid_Lock);

seq_printf(m,"Security type: %s\n", get_security_type_str(server->ops->select_sectype(server, ses->sectype)));