Hi John, Ingo
As still we are seeing race between do_task_stat and do_exit of task,
Can't we have to
put more strict check in case, if stack pointer is NULL in below code :
if (permitted && (task->flags & PF_DUMPCORE)) {
eip = KSTK_EIP(task);
esp = KSTK_ESP(task);
}
Regards
Gaurav
On 1/9/2018 7:03 PM, Kohli, Gaurav wrote:
HI ,
We are seeing crash in do_task_stat while accessing stack pointer, It
seems same task has already completed do_exit call.
So it seems a race between them:
Below is the crash trace:
49750.534377] Kernel BUG at ffffff8e7a4c53a8 [verbose debug info
unavailable]
[49750.534394] task: ffffffe7b4475580 task.stack: ffffffe7a5f0c000
[49750.534400] PC is at do_task_stat+0x740/0x908
[49750.534402] LR is at do_task_stat+0xa4/0x908
[49750.534403] pc : [<ffffff8e7a4c53a8>] lr : [<ffffff8e7a4c4d0c>]
pstate: 80400145
[49750.534404] sp : ffffffe7a5f0fbd0
and here is stack trace on that core:
-000|user_stack_pointer(inline)
-000|do_task_stat(
| m = 0xFFFFFFE7A5CD7380,
| ns = 0xFFFFFF8E7C43C748,
| ?,
| task = 0xFFFFFFE80D8C2280,
| ?)
| tty_pgrp = 0
| ppid = 2084696064
| sid = 0
| mm = 0xFFFFFFE7B4424140
| tcomm = (84, 9, 71, 122, 142, 255, 255, 255, 48, 253, 240, 165,
231, 255, 255, 255)
| flags = 18446743969119403392
-001|proc_tgid_stat(
| m = 0xFFFFFFE7A5CD7380,
| ?,
Below are task stats which shows , process completed the do_exit call:
struct task_struct.flags -x 0xFFFFFFE80D8C2280
flags = 0x40870c
crash_64> struct task_struct.exit_code -x 0xFFFFFFE80D8C2280
exit_code = 0x6
struct task_struct.state -x 0xFFFFFFE80D8C2280
state = 0x40
In our build both patches are there ,
fs/proc: report eip/esp in /prod/PID/stat for coredumping
and also task.state has already set PF_DUMPCORE as it got the sigabrt
signal.
Regards
Gaurav
-- Qualcomm India Private Limited, on behalf of Qualcomm Innovation
Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation
Collaborative Project.
-- Qualcomm India Private Limited, on behalf of Qualcomm Innovation
Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation
Collaborative Project.
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