4.4-stable review patch. If anyone has any objections, please let me know.
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From: Steven Rostedt (VMware) rostedt@goodmis.org
commit 2519c1bbe38d7acacc9aacba303ca6f97482ed53 upstream.
Commit 57ea2a34adf4 ("tracing/kprobes: Fix trace_probe flags on enable_trace_kprobe() failure") added an if statement that depends on another if statement that gcc doesn't see will initialize the "link" variable and gives the warning:
"warning: 'link' may be used uninitialized in this function"
It is really a false positive, but to quiet the warning, and also to make sure that it never actually is used uninitialized, initialize the "link" variable to NULL and add an if (!WARN_ON_ONCE(!link)) where the compiler thinks it could be used uninitialized.
Cc: stable@vger.kernel.org Fixes: 57ea2a34adf4 ("tracing/kprobes: Fix trace_probe flags on enable_trace_kprobe() failure") Reported-by: kbuild test robot lkp@intel.com Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/trace/trace_kprobe.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
--- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -349,7 +349,7 @@ static struct trace_kprobe *find_trace_k static int enable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file) { - struct event_file_link *link; + struct event_file_link *link = NULL; int ret = 0;
if (file) { @@ -375,7 +375,9 @@ enable_trace_kprobe(struct trace_kprobe
if (ret) { if (file) { - list_del_rcu(&link->list); + /* Notice the if is true on not WARN() */ + if (!WARN_ON_ONCE(!link)) + list_del_rcu(&link->list); kfree(link); tk->tp.flags &= ~TP_FLAG_TRACE; } else {