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authorSteven Rostedt (Google)2022-03-08 10:39:45 -0500
committerSteven Rostedt (Google)2022-03-10 17:41:18 -0500
commit5677a3d713ad795e3ce32d631941e982777b43db (patch)
tree3721f7325edb65ffe1d2484da43a39a3e9574b04 /kernel/trace
parent173c2049d12b441b498d6423276f5dd76b1e637b (diff)
tracing: Fix last_cmd_set() string management in histogram code
Using strnlen(dest, str, n) is confusing, as the size of dest must be strlen(dest) + n + 1. Even more confusing, using sizeof(string constant) gives you strlen(string constant) + 1 and not just strlen(). These two together made using strncat() with a constant string a bit off in the calculations as we have: len = sizeof(HIST_PREFIX) + strlen(str) + 1; kfree(last_cmd); last_cmd = kzalloc(len, GFP_KERNEL); strcpy(last_cmd, HIST_PREFIX); len -= sizeof(HIST_PREFIX) + 1; strncat(last_cmd, str, len); The above works if we s/sizeof/strlen/ with HIST_PREFIX (which is defined as "hist:", but because sizeof(HIST_PREFIX) is equal to strlen(HIST_PREFIX) + 1, we can drop the +1 in the code. But at least comment that we are doing so. Link: https://lore.kernel.org/all/202203082112.Iu7tvFl4-lkp@intel.com/ Fixes: 9f8e5aee93ed2 ("tracing: Fix allocation of last_cmd in last_cmd_set()") Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/trace_events_hist.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 78788049f3d3..954b19e2f196 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -749,14 +749,16 @@ static void last_cmd_set(struct trace_event_file *file, char *str)
if (!str)
return;
- len = sizeof(HIST_PREFIX) + strlen(str) + 1;
+ /* sizeof() contains the nul byte */
+ len = sizeof(HIST_PREFIX) + strlen(str);
kfree(last_cmd);
last_cmd = kzalloc(len, GFP_KERNEL);
if (!last_cmd)
return;
strcpy(last_cmd, HIST_PREFIX);
- len -= sizeof(HIST_PREFIX) + 1;
+ /* Again, sizeof() contains the nul byte */
+ len -= sizeof(HIST_PREFIX);
strncat(last_cmd, str, len);
if (file) {