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author | Masami Hiramatsu (Google) <mhiramat@kernel.org> | 2023-07-07 16:03:19 +0200 |
---|---|---|
committer | Masami Hiramatsu (Google) <mhiramat@kernel.org> | 2023-07-11 02:17:01 +0200 |
commit | 195b9cb5b288fec1c871ef89f78cc9a7461aad3a (patch) | |
tree | e2e4739f378177d8a1dfd5e37708c062b2d5384c /kernel/trace/rethook.c | |
parent | kernel: kprobes: Remove unnecessary ‘0’ values (diff) | |
download | linux-195b9cb5b288fec1c871ef89f78cc9a7461aad3a.tar.xz linux-195b9cb5b288fec1c871ef89f78cc9a7461aad3a.zip |
fprobe: Ensure running fprobe_exit_handler() finished before calling rethook_free()
Ensure running fprobe_exit_handler() has finished before
calling rethook_free() in the unregister_fprobe() so that caller can free
the fprobe right after unregister_fprobe().
unregister_fprobe() ensured that all running fprobe_entry/exit_handler()
have finished by calling unregister_ftrace_function() which synchronizes
RCU. But commit 5f81018753df ("fprobe: Release rethook after the ftrace_ops
is unregistered") changed to call rethook_free() after
unregister_ftrace_function(). So call rethook_stop() to make rethook
disabled before unregister_ftrace_function() and ensure it again.
Here is the possible code flow that can call the exit handler after
unregister_fprobe().
------
CPU1 CPU2
call unregister_fprobe(fp)
...
__fprobe_handler()
rethook_hook() on probed function
unregister_ftrace_function()
return from probed function
rethook hooks
find rh->handler == fprobe_exit_handler
call fprobe_exit_handler()
rethook_free():
set rh->handler = NULL;
return from unreigster_fprobe;
call fp->exit_handler() <- (*)
------
(*) At this point, the exit handler is called after returning from
unregister_fprobe().
This fixes it as following;
------
CPU1 CPU2
call unregister_fprobe()
...
rethook_stop():
set rh->handler = NULL;
__fprobe_handler()
rethook_hook() on probed function
unregister_ftrace_function()
return from probed function
rethook hooks
find rh->handler == NULL
return from rethook
rethook_free()
return from unreigster_fprobe;
------
Link: https://lore.kernel.org/all/168873859949.156157.13039240432299335849.stgit@devnote2/
Fixes: 5f81018753df ("fprobe: Release rethook after the ftrace_ops is unregistered")
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace/rethook.c')
-rw-r--r-- | kernel/trace/rethook.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c index 60f6cb2b486b..468006cce7ca 100644 --- a/kernel/trace/rethook.c +++ b/kernel/trace/rethook.c @@ -54,6 +54,19 @@ static void rethook_free_rcu(struct rcu_head *head) } /** + * rethook_stop() - Stop using a rethook. + * @rh: the struct rethook to stop. + * + * Stop using a rethook to prepare for freeing it. If you want to wait for + * all running rethook handler before calling rethook_free(), you need to + * call this first and wait RCU, and call rethook_free(). + */ +void rethook_stop(struct rethook *rh) +{ + WRITE_ONCE(rh->handler, NULL); +} + +/** * rethook_free() - Free struct rethook. * @rh: the struct rethook to be freed. * |