On Wed, 1 Nov 2023 17:12:53 -0700 Richard Cochran wrote:

quoted

There is no lock protection when writing ptp->tsevqs in ptp_open(),
ptp_release(), which can cause data corruption,

Really?  How?

Let me show the corruption that occurs in ptp_open() and ptp_release(), 

1. Corruption that appears in ptp_open(),
Link: https://syzkaller.appspot.com/bug?extid=df3f3ef31f60781fa911

list_add corruption. prev->next should be next (ffff88814a1325e8), but was ffff888078d25048. (prev=ffff888078d21048).
------------[ cut here ]------------
kernel BUG at lib/list_debug.c:32!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 7237 Comm: syz-executor182 Not tainted 6.6.0-rc6-next-20231020-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
RIP: 0010:__list_add_valid_or_report+0xb6/0x100 lib/list_debug.c:32
Code: e8 2f a5 3a fd 0f 0b 48 89 d9 48 c7 c7 40 9d e9 8a e8 1e a5 3a fd 0f 0b 48 89 f1 48 c7 c7 c0 9d e9 8a 48 89 de e8 0a a5 3a fd <0f> 0b 48 89 f2 48 89 d9 48 89 ee 48 c7 c7 40 9e e9 8a e8 f3 a4 3a
RSP: 0018:ffffc90009b3f898 EFLAGS: 00010286
RAX: 0000000000000075 RBX: ffff88814a1325e8 RCX: ffffffff816bb8d9
RDX: 0000000000000000 RSI: ffffffff816c4d42 RDI: 0000000000000005
RBP: ffff88807c7a9048 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000080000000 R11: 0000000000000001 R12: ffff88814a132000
R13: ffffc90009b3f900 R14: ffff888078d21048 R15: ffff88807c7a9048
FS:  0000555556c00380(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffef0aa1138 CR3: 000000007d17e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __list_add_valid include/linux/list.h:88 [inline]
 __list_add include/linux/list.h:150 [inline]
 list_add_tail include/linux/list.h:183 [inline]
 ptp_open+0x1c5/0x4f0 drivers/ptp/ptp_chardev.c:122
 posix_clock_open+0x17e/0x240 kernel/time/posix-clock.c:134
 chrdev_open+0x26d/0x6e0 fs/char_dev.c:414
 do_dentry_open+0x8d4/0x18d0 fs/open.c:948
 do_open fs/namei.c:3621 [inline]
 path_openat+0x1d36/0x2cd0 fs/namei.c:3778
 do_filp_open+0x1dc/0x430 fs/namei.c:3808
 do_sys_openat2+0x176/0x1e0 fs/open.c:1440
 do_sys_open fs/open.c:1455 [inline]
 __do_sys_openat fs/open.c:1471 [inline]
 __se_sys_openat fs/open.c:1466 [inline]
 __x64_sys_openat+0x175/0x210 fs/open.c:1466
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0x6b
RIP: 0033:0x7fc6c2099ae9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffef0aa1238 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fc6c2099ae9
RDX: 0000000000000000 RSI: 0000000020000300 RDI: ffffffffffffff9c
RBP: 00000000000f4240 R08: 0000000000000000 R09: 00000000000000a0
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000000130fc
R13: 00007ffef0aa124c R14: 00007ffef0aa1260 R15: 00007ffef0aa1250
 </TASK>

2. Corruption that appears in ptp_open(),
Link: https://syzkaller.appspot.com/x/log.txt?x=169a58d1680000

list_del corruption. prev->next should be ffff8880280e5048, but was ffff888025dc1048. (prev=ffff88814adb1048)
------------[ cut here ]------------
kernel BUG at lib/list_debug.c:62!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 13142 Comm: syz-executor.2 Not tainted 6.6.0-rc6-next-20231018-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
RIP: 0010:__list_del_entry_valid_or_report+0x11f/0x1b0
Code: 8f e9 8a e8 c3 d3 3a fd 0f 0b 48 89 ca 48 c7 c7 e0 8f e9 8a e8 b2 d3 3a fd 0f 0b 48 89 c2 48 c7 c7 40 90 e9 8a e8 a1 d3 3a fd <0f> 0b 48 89 d1 48 c7 c7 c0 90 e9 8a 48 89 c2 e8 8d d3 3a fd 0f 0b
RSP: 0018:ffffc90003167e08 EFLAGS: 00010086
RAX: 000000000000006d RBX: ffff8880280e4000 RCX: ffffffff816b9cd9
RDX: 0000000000000000 RSI: ffffffff816c3142 RDI: 0000000000000005
RBP: ffff888023b7c480 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000080000001 R11: 0000000000000001 R12: 0000000000000293
R13: ffff8880280e5008 R14: ffff8880280e5048 R15: ffff8880280e5050
FS:  00005555557e3480(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f350fd98000 CR3: 000000002427a000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ptp_release+0xca/0x2a0
 posix_clock_release+0xa4/0x160
 __fput+0x270/0xbb0
 __fput_sync+0x47/0x50
 __x64_sys_close+0x87/0xf0
 do_syscall_64+0x3f/0x110
 entry_SYSCALL_64_after_hwframe+0x63/0x6b 


The above two logs can clearly indicate that there is corruption when 
executing the operation of writing ptp->tsevqs in ptp_open() and ptp_release().

quoted

use mutex lock to avoid this
issue.

Moreover, ptp_release() should not be used to release the queue in ptp_read(),
and it should be deleted together.

Reported-and-tested-by: syzbot+df3f3ef31f60781fa911@syzkaller.appspotmail.com
Fixes: 8f5de6fb2453 ("ptp: support multiple timestamp event readers")
Signed-off-by: Edward Adam Davis <redacted>
---
 drivers/ptp/ptp_chardev.c | 11 +++++++++--
 drivers/ptp/ptp_clock.c   |  3 +++
 drivers/ptp/ptp_private.h |  1 +
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
index 282cd7d24077..e31551d2697d 100644
--- a/drivers/ptp/ptp_chardev.c
+++ b/drivers/ptp/ptp_chardev.c

@@ -109,6 +109,9 @@ int ptp_open(struct posix_clock_context *pccontext, fmode_t fmode)
 	struct timestamp_event_queue *queue;
 	char debugfsname[32];

+	if (mutex_lock_interruptible(&ptp->tsevq_mux))
+		return -ERESTARTSYS;
+

This mutex is not needed.

Please don't ignore review comments.

Thanks,
edward