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| author | Qiu Peiyang <peiyangx.qiu@intel.com> | 2015-12-31 13:11:28 +0800 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2016-01-04 15:22:47 -0500 |
| commit | f36d1be2930ede0a1947686e1126ffda5d5ee1bb (patch) | |
| tree | 85c575aeb6241c5740981aea83cd1d44fe74f61a /kernel | |
| parent | 713a3e4de707fab49d5aa4bceb77db1058572a7b (diff) | |
| download | lwn-f36d1be2930ede0a1947686e1126ffda5d5ee1bb.tar.gz lwn-f36d1be2930ede0a1947686e1126ffda5d5ee1bb.zip | |
tracing: Fix setting of start_index in find_next()
When we do cat /sys/kernel/debug/tracing/printk_formats, we hit kernel
panic at t_show.
general protection fault: 0000 [#1] PREEMPT SMP
CPU: 0 PID: 2957 Comm: sh Tainted: G W O 3.14.55-x86_64-01062-gd4acdc7 #2
RIP: 0010:[<ffffffff811375b2>]
[<ffffffff811375b2>] t_show+0x22/0xe0
RSP: 0000:ffff88002b4ebe80 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000004
RDX: 0000000000000004 RSI: ffffffff81fd26a6 RDI: ffff880032f9f7b1
RBP: ffff88002b4ebe98 R08: 0000000000001000 R09: 000000000000ffec
R10: 0000000000000000 R11: 000000000000000f R12: ffff880004d9b6c0
R13: 7365725f6d706400 R14: ffff880004d9b6c0 R15: ffffffff82020570
FS: 0000000000000000(0000) GS:ffff88003aa00000(0063) knlGS:00000000f776bc40
CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00000000f6c02ff0 CR3: 000000002c2b3000 CR4: 00000000001007f0
Call Trace:
[<ffffffff811dc076>] seq_read+0x2f6/0x3e0
[<ffffffff811b749b>] vfs_read+0x9b/0x160
[<ffffffff811b7f69>] SyS_read+0x49/0xb0
[<ffffffff81a3a4b9>] ia32_do_call+0x13/0x13
---[ end trace 5bd9eb630614861e ]---
Kernel panic - not syncing: Fatal exception
When the first time find_next calls find_next_mod_format, it should
iterate the trace_bprintk_fmt_list to find the first print format of
the module. However in current code, start_index is smaller than *pos
at first, and code will not iterate the list. Latter container_of will
get the wrong address with former v, which will cause mod_fmt be a
meaningless object and so is the returned mod_fmt->fmt.
This patch will fix it by correcting the start_index. After fixed,
when the first time calls find_next_mod_format, start_index will be
equal to *pos, and code will iterate the trace_bprintk_fmt_list to
get the right module printk format, so is the returned mod_fmt->fmt.
Link: http://lkml.kernel.org/r/5684B900.9000309@intel.com
Cc: stable@vger.kernel.org # 3.12+
Fixes: 102c9323c35a8 "tracing: Add __tracepoint_string() to export string pointers"
Signed-off-by: Qiu Peiyang <peiyangx.qiu@intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/trace/trace_printk.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/trace/trace_printk.c b/kernel/trace/trace_printk.c index 1c2b28536feb..060df67dbdd1 100644 --- a/kernel/trace/trace_printk.c +++ b/kernel/trace/trace_printk.c @@ -273,6 +273,7 @@ static const char **find_next(void *v, loff_t *pos) if (*pos < last_index + start_index) return __start___tracepoint_str + (*pos - last_index); + start_index += last_index; return find_next_mod_format(start_index, v, fmt, pos); } |