lkml.org 
[lkml]   [2022]   [Nov]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] tracing: Fix potential null-pointer-access of entry in list 'tr->err_log'
Date
Entries in list 'tr->err_log' will be reused after entry number
exceed TRACING_LOG_ERRS_MAX.

The cmd string of the to be reused entry will be freed first then
allocated a new one. If the allocation failed, then the entry will
still be in list 'tr->err_log' but its 'cmd' field is set to be NULL,
later access of 'cmd' is risky.

Currently above problem can cause the loss of 'cmd' information of first
entry in 'tr->err_log'. When execute `cat /sys/kernel/tracing/error_log`,
reproduce logs like:
[ 37.495100] trace_kprobe: error: Maxactive is not for kprobe(null) ^
[ 38.412517] trace_kprobe: error: Maxactive is not for kprobe
Command: p4:myprobe2 do_sys_openat2
^

Fixes: 1581a884b7ca ("tracing: Remove size restriction on tracing_log_err cmd strings")
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
---
kernel/trace/trace.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 47a44b055a1d..5ae776598106 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -7802,6 +7802,7 @@ static struct tracing_log_err *get_tracing_log_err(struct trace_array *tr,
int len)
{
struct tracing_log_err *err;
+ char *cmd;

if (tr->n_err_log_entries < TRACING_LOG_ERRS_MAX) {
err = alloc_tracing_log_err(len);
@@ -7810,12 +7811,12 @@ static struct tracing_log_err *get_tracing_log_err(struct trace_array *tr,

return err;
}
-
+ cmd = kzalloc(len, GFP_KERNEL);
+ if (!cmd)
+ return ERR_PTR(-ENOMEM);
err = list_first_entry(&tr->err_log, struct tracing_log_err, list);
kfree(err->cmd);
- err->cmd = kzalloc(len, GFP_KERNEL);
- if (!err->cmd)
- return ERR_PTR(-ENOMEM);
+ err->cmd = cmd;
list_del(&err->list);

return err;
--
2.25.1
\
 
 \ /
  Last update: 2022-11-14 11:46    [W:0.059 / U:0.120 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site