39a979c6e2
commit 9f0bbf3115ca9f91f43b7c74e9ac7d79f47fc6c2 upstream.
Because there may be random garbage beyond a string's null terminator,
it's not correct to copy the the complete character array for use as a
hist trigger key. This results in multiple histogram entries for the
'same' string key.
So, in the case of a string key, use strncpy instead of memcpy to
avoid copying in the extra bytes.
Before, using the gdbus entries in the following hist trigger as an
example:
# echo 'hist:key=comm' > /sys/kernel/debug/tracing/events/sched/sched_waking/trigger
# cat /sys/kernel/debug/tracing/events/sched/sched_waking/hist
...
{ comm: ImgDecoder #4 } hitcount: 203
{ comm: gmain } hitcount: 213
{ comm: gmain } hitcount: 216
{ comm: StreamTrans #73 } hitcount: 221
{ comm: mozStorage #3 } hitcount: 230
{ comm: gdbus } hitcount: 233
{ comm: StyleThread#5 } hitcount: 253
{ comm: gdbus } hitcount: 256
{ comm: gdbus } hitcount: 260
{ comm: StyleThread#4 } hitcount: 271
...
# cat /sys/kernel/debug/tracing/events/sched/sched_waking/hist | egrep gdbus | wc -l
51
After:
# cat /sys/kernel/debug/tracing/events/sched/sched_waking/hist | egrep gdbus | wc -l
1
Link: http://lkml.kernel.org/r/50c35ae1267d64eee975b8125e151e600071d4dc.1549309756.git.tom.zanussi@linux.intel.com
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: stable@vger.kernel.org
Fixes: 79e577cbce4c4 ("tracing: Support string type key properly")
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.