From: Zheng Yejian zhengyejian1@huawei.com

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-zhengyej...

Cc: stable@vger.kernel.org Cc: mhiramat@kernel.org Cc: mark.rutland@arm.com Cc: ast@kernel.org Cc: daniel@iogearbox.net Fixes: 8a141dd7f706 ("ftrace: Fix modify_ftrace_direct.") Signed-off-by: Zheng Yejian zhengyejian1@huawei.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org --- 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--; + } }

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