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ptp: Fixes a null pointer dereference in ptp_ioctl

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Syzkaller found a null pointer dereference in ptp_ioctl
originating from the lack of a null check for tsevq.

```
general protection fault, probably for non-canonical
	address 0xdffffc000000020b: 0000 [#1] PREEMPT SMP KASAN
KASAN: probably user-memory-access in range
	[0x0000000000001058-0x000000000000105f]
CPU: 0 PID: 5053 Comm: syz-executor353 Not tainted
	6.6.0-syzkaller-10396-g4652b8e4f3ff #0
Hardware name: Google Google Compute Engine/Google Compute Engine,
	BIOS Google 10/09/2023
RIP: 0010:ptp_ioctl+0xcb7/0x1d10 drivers/ptp/ptp_chardev.c:476
...
Call Trace:
 <TASK>
 posix_clock_ioctl+0xf8/0x160 kernel/time/posix-clock.c:86
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:871 [inline]
 __se_sys_ioctl fs/ioctl.c:857 [inline]
 __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857
 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
```

This patch fixes the issue by adding a check for tsevq and
ensuring ptp_ioctl returns with an error if tsevq is null.

Reported-by: syzbot+8a78ecea7ac1a2ea26e5@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=8a78ecea7ac1a2ea26e5
Fixes: c5a445b1e9 ("ptp: support event queue reader channel masks")
Signed-off-by: Yuran Pereira <yuran.pereira@hotmail.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yuran Pereira 2023-11-08 02:18:36 +05:30 committed by David S. Miller
parent 89cdf9d556
commit 8a4f030dbc
1 changed files with 2 additions and 0 deletions
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2
drivers/ptp/ptp_chardev.c
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@ -176,6 +176,8 @@ long ptp_ioctl(struct posix_clock_context *pccontext, unsigned int cmd,
int enable, err = 0;
tsevq = pccontext->private_clkdata;
if (!tsevq)
return -EINVAL;
switch (cmd) {