hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IAA3U5 CVE: NA

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After commit 5e66a5bdad69 ("ftrace: Fix rcu warn in ftrace_location()"), syzkaller reports following warning:

WARNING: lock held when returning to user space! 4.18.0+ #16 Tainted: G W ---------r- - ------------------------------------------------ modprobe/4255 is leaving the kernel with locks still held! 1 lock held by modprobe/4255: #0: 0000000012ba3568 (rcu_read_lock){....}, at: ftrace_location_range+0x292/0x440 BUG: scheduling while atomic: modprobe/4255/0x00000002 ============================= BUG: scheduling while atomic: modprobe/4256/0x00000002 INFO: lockdep is turned off. Modules linked in: Kernel panic - not syncing: scheduling while atomic

It seems that rcu_read_lock() is held but rcu_read_unlock() is not called, this is most likely due to the inconsistent state when calling in_atomic(). To fix it, use preemt_{disable,enable}_notrace() instead of rcu_read_{,un}lock().

Fixes: 5e66a5bdad69 ("ftrace: Fix rcu warn in ftrace_location()") Signed-off-by: Zheng Yejian zhengyejian1@huawei.com --- kernel/trace/ftrace.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index ad4440da5b78..ceb4bab432f1 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -1581,12 +1581,7 @@ unsigned long ftrace_location_range(unsigned long start, unsigned long end) key.ip = start; key.flags = end; /* overload flags, as it is unsigned long */

- /* - * It is in atomic context when called from ftrace_int3_handler(), - * in this case rcu lock is not needed. - */ - if (!in_atomic()) - rcu_read_lock(); + preempt_disable_notrace(); for (pg = ftrace_pages_start; pg; pg = pg->next) { if (pg->index == 0 || end < pg->records[0].ip || @@ -1600,8 +1595,7 @@ unsigned long ftrace_location_range(unsigned long start, unsigned long end) break; } } - if (!in_atomic()) - rcu_read_unlock(); + preempt_enable_notrace();

return ip; }