3:33 a.m.
Hi Lianbo
On Sat, Aug 8, 2020 at 10:46 PM lijiang <lijiang(a)redhat.com> wrote:
在 2020年08月07日 00:00, crash-utility-request(a)redhat.com 写道:
> Message: 5
> Date: Thu, 6 Aug 2020 09:30:22 -0400
> From: Dave Wysochanski <dwysocha(a)redhat.com>
> To: crash-utility(a)redhat.com
> Subject: [Crash-utility] [PATCH v3] Fix "log" command when crash is
> started with "--minimal" option
> Message-ID: <20200806133022.2127538-1-dwysocha(a)redhat.com>
>
> Commit c86250bce29f introduced the useful '-T' option to print the
> log timestamp in human-readable form. However, this option does
> not work when crash is invoked with '--minimal' mode, and if tried,
> crash will spin at 100% and continuously crash at a divide by 0
> because machdep->hz == 0.
>
> Fix this by disallowing this option in minimal mode. In addition,
> only calculate the logic to calculate kt->boot_date.tv_sec
> when this option is enabled.
>
Hi, Dave Wysochanski
Thank you for the patch.
> Fixes: c86250bce29f ("Introduction of the "log -T" option...")
> Signed-off-by: Dave Wysochanski <dwysocha(a)redhat.com>
> Reviewed-by: Wang Long <w(a)laoqinren.net>
> Tested-by: Mathias Krause <minipli(a)grsecurity.net>
> ---
> kernel.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/kernel.c b/kernel.c
> index 5ed6021..95119f3 100644
> --- a/kernel.c
> +++ b/kernel.c
> @@ -4939,7 +4939,10 @@ cmd_log(void)
> if (argerrs)
> cmd_usage(pc->curcmd, SYNOPSIS);
>
> - if (kt->boot_date.tv_sec == 0) {
> + if (msg_flags & SHOW_LOG_CTIME && pc->flags &
MINIMAL_MODE)
> + error(FATAL, "log: option 'T' not available in minimal
mode\n");
> +
> + if (msg_flags & SHOW_LOG_CTIME && kt->boot_date.tv_sec == 0) {
The above two 'if' statements have the same checking condition, would you mind
putting them together
as a statement block? E.g:
Sure I can resubmit a fixup of v4 patch once there are no more changes needed.
+ if (msg_flags & SHOW_LOG_CTIME) {
+ if (pc->flags & MINIMAL_MODE) {
+ error(WARNING, "the option '-T' not available in
minimal mode\n");
+ return;
+ }
+
+ if (kt->boot_date.tv_sec == 0) {
...
+ }
}
In addition, might it be more reasonable to issue a warning instead of a fatal error?
If you use WARNING it will not fix the infinite loop / CPU spin at
100%. You have to CTRL-C the crash program to get the prompt back.
So I do not think this is a good idea.
This is easily reproducible on any vmcore you can see for yourself if
you want. But here is the backtrace in GDB:
crash> log -T
[Detaching after fork from child process 2669642]
log: WARNING: log: option 'T' not available in minimal mode
Program received signal SIGFPE, Arithmetic exception.
0x00000000004e5ecf in cmd_log () at kernel.c:4950
4950 kt->boot_date.tv_sec = kt->date.tv_sec - uptime_sec;
Missing separate debuginfos, use: yum debuginfo-install
zlib-1.2.11-13.el8.x86_64
(gdb) bt
#0 0x00000000004e5ecf in cmd_log () at kernel.c:4950
#1 0x0000000000463ea9 in exec_command () at main.c:880
#2 0x00000000004640da in main_loop () at main.c:827
#3 0x00000000006c0ce3 in captured_command_loop (data=<optimized out>)
at main.c:258
#4 0x00000000006bf5ce in catch_errors (func=0x6c0cd0
<captured_command_loop>, func_args=0x0, errstring=0x91b926 "", mask=6)
at exceptions.c:557
#5 0x00000000006c1bb6 in captured_main (data=<optimized out>) at main.c:1064
#6 0x00000000006bf5ce in catch_errors (func=0x6c0df0 <captured_main>,
func_args=0x7fffffffe260, errstring=0x91b926 "", mask=6) at
exceptions.c:557
#7 0x00000000006c0ae4 in gdb_main (args=<optimized out>) at main.c:1079
#8 0x00000000006c0b1e in gdb_main_entry (argc=<optimized out>,
argv=<optimized out>, argv@entry=0x7fffffffe3c8) at main.c:1099
#9 0x00000000004f86d4 in gdb_main_loop (argc=<optimized out>,
argc@entry=4, argv=argv@entry=0x7fffffffe3c8) at gdb_interface.c:76
#10 0x0000000000462707 in main (argc=4, argv=0x7fffffffe3c8) at main.c:708
(gdb) c
Continuing.
Program received signal SIGFPE, Arithmetic exception.
0x00000000004e5ecf in cmd_log () at kernel.c:4950
4950 kt->boot_date.tv_sec = kt->date.tv_sec - uptime_sec;
(gdb) bt
#0 0x00000000004e5ecf in cmd_log () at kernel.c:4950
#1 0x0000000000463ea9 in exec_command () at main.c:880
#2 0x00000000004640da in main_loop () at main.c:827
#3 0x00000000006c0ce3 in captured_command_loop (data=<optimized out>)
at main.c:258
#4 0x00000000006bf5ce in catch_errors (func=0x6c0cd0
<captured_command_loop>, func_args=0x0, errstring=0x91b926 "", mask=6)
at exceptions.c:557
#5 0x00000000006c1bb6 in captured_main (data=<optimized out>) at main.c:1064
#6 0x00000000006bf5ce in catch_errors (func=0x6c0df0 <captured_main>,
func_args=0x7fffffffe260, errstring=0x91b926 "", mask=6) at
exceptions.c:557
#7 0x00000000006c0ae4 in gdb_main (args=<optimized out>) at main.c:1079
#8 0x00000000006c0b1e in gdb_main_entry (argc=<optimized out>,
argv=<optimized out>, argv@entry=0x7fffffffe3c8) at main.c:1099
#9 0x00000000004f86d4 in gdb_main_loop (argc=<optimized out>,
argc@entry=4, argv=argv@entry=0x7fffffffe3c8) at gdb_interface.c:76
#10 0x0000000000462707 in main (argc=4, argv=0x7fffffffe3c8) at main.c:708
(gdb) quit
A debugging session is active.
Inferior 1 [process 2669636] will be killed.
Quit anyway? (y or n) y