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| author | Steven Rostedt (Red Hat) <rostedt@goodmis.org> | 2016-06-17 16:10:42 -0400 |
|---|---|---|
| committer | Sasha Levin <sasha.levin@oracle.com> | 2016-07-12 08:46:57 -0400 |
| commit | 673a67b97ccc29cd7c34aded3b832387eb40d71e (patch) | |
| tree | 3bf2f55cc4cbffd06021de9c009aab185cdfc19b /kernel | |
| parent | 5c6fe0bcd209d7b89a7b781c76992b290739cc4e (diff) | |
| download | lwn-673a67b97ccc29cd7c34aded3b832387eb40d71e.tar.gz lwn-673a67b97ccc29cd7c34aded3b832387eb40d71e.zip | |
tracing: Handle NULL formats in hold_module_trace_bprintk_format()
[ Upstream commit 70c8217acd4383e069fe1898bbad36ea4fcdbdcc ]
If a task uses a non constant string for the format parameter in
trace_printk(), then the trace_printk_fmt variable is set to NULL. This
variable is then saved in the __trace_printk_fmt section.
The function hold_module_trace_bprintk_format() checks to see if duplicate
formats are used by modules, and reuses them if so (saves them to the list
if it is new). But this function calls lookup_format() that does a strcmp()
to the value (which is now NULL) and can cause a kernel oops.
This wasn't an issue till 3debb0a9ddb ("tracing: Fix trace_printk() to print
when not using bprintk()") which added "__used" to the trace_printk_fmt
variable, and before that, the kernel simply optimized it out (no NULL value
was saved).
The fix is simply to handle the NULL pointer in lookup_format() and have the
caller ignore the value if it was NULL.
Link: http://lkml.kernel.org/r/1464769870-18344-1-git-send-email-zhengjun.xing@intel.com
Reported-by: xingzhen <zhengjun.xing@intel.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Fixes: 3debb0a9ddb ("tracing: Fix trace_printk() to print when not using bprintk()")
Cc: stable@vger.kernel.org # v3.5+
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/trace/trace_printk.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/kernel/trace/trace_printk.c b/kernel/trace/trace_printk.c index 14ffaa59a9e9..9008103db583 100644 --- a/kernel/trace/trace_printk.c +++ b/kernel/trace/trace_printk.c @@ -38,6 +38,10 @@ struct trace_bprintk_fmt { static inline struct trace_bprintk_fmt *lookup_format(const char *fmt) { struct trace_bprintk_fmt *pos; + + if (!fmt) + return ERR_PTR(-EINVAL); + list_for_each_entry(pos, &trace_bprintk_fmt_list, list) { if (!strcmp(pos->fmt, fmt)) return pos; @@ -59,7 +63,8 @@ void hold_module_trace_bprintk_format(const char **start, const char **end) for (iter = start; iter < end; iter++) { struct trace_bprintk_fmt *tb_fmt = lookup_format(*iter); if (tb_fmt) { - *iter = tb_fmt->fmt; + if (!IS_ERR(tb_fmt)) + *iter = tb_fmt->fmt; continue; } |