From: Zheng Yejian <zhengyejian1@xxxxxxxxxx> Syzkaller report a WARNING: "WARN_ON(!direct)" in modify_ftrace_direct(). Root cause is 'direct->addr' was changed from 'old_addr' to 'new_addr' but not restored if error happened on calling ftrace_modify_direct_caller(). Then it can no longer find 'direct' by that 'old_addr'. To fix it, restore 'direct->addr' to 'old_addr' explicitly in error path. Link: https://lore.kernel.org/linux-trace-kernel/20230330025223.1046087-1-zhengyejian1@xxxxxxxxxx Cc: stable@xxxxxxxxxxxxxxx Cc: <mhiramat@xxxxxxxxxx> Cc: <mark.rutland@xxxxxxx> Cc: <ast@xxxxxxxxxx> Cc: <daniel@xxxxxxxxxxxxx> Fixes: 8a141dd7f706 ("ftrace: Fix modify_ftrace_direct.") Signed-off-by: Zheng Yejian <zhengyejian1@xxxxxxxxxx> Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> --- kernel/trace/ftrace.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 0feea145bb29..c67bcc89a771 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5667,12 +5667,15 @@ int modify_ftrace_direct(unsigned long ip, ret = 0; } - if (unlikely(ret && new_direct)) { - direct->count++; - list_del_rcu(&new_direct->next); - synchronize_rcu_tasks(); - kfree(new_direct); - ftrace_direct_func_count--; + if (ret) { + direct->addr = old_addr; + if (unlikely(new_direct)) { + direct->count++; + list_del_rcu(&new_direct->next); + synchronize_rcu_tasks(); + kfree(new_direct); + ftrace_direct_func_count--; + } } out_unlock: -- 2.39.2
