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| author | Steven Rostedt (Google) <rostedt@goodmis.org> | 2022-03-08 18:39:45 +0300 |
|---|---|---|
| committer | Steven Rostedt (Google) <rostedt@goodmis.org> | 2022-03-11 01:41:18 +0300 |
| commit | 5677a3d713ad795e3ce32d631941e982777b43db (patch) | |
| tree | 3721f7325edb65ffe1d2484da43a39a3e9574b04 /kernel/trace | |
| parent | 173c2049d12b441b498d6423276f5dd76b1e637b (diff) | |
| download | linux-5677a3d713ad795e3ce32d631941e982777b43db.tar.xz | |
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.c | 6 |
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) { |