Messages in this thread Patch in this message | | | From | Tetsuo Handa <> | Subject | [PATCH] tracepoint: Do not warn on EEXIST or ENOENT | Date | Sat, 26 Jun 2021 22:58:45 +0900 |
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syzbot is hitting WARN_ON_ONCE() at tracepoint_add_func() [1], but func_add() returning -EEXIST and func_remove() returning -ENOENT are not kernel bugs that can justify crashing the system.
Commit d66a270be3310d7a ("tracepoint: Do not warn on ENOMEM") says that tracepoint should only warn when a kernel API user does not respect the required preconditions (e.g. same tracepoint enabled twice, or called to remove a tracepoint that does not exist). But WARN*() must be used to denote kernel bugs and not to print simple warnings. If someone wants to print warnings, pr_warn() etc. should be used instead.
Link: https://syzkaller.appspot.com/bug?id=41f4318cf01762389f4d1c1c459da4f542fe5153 [1] Reported-by: syzbot <syzbot+721aa903751db87aa244@syzkaller.appspotmail.com> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Tested-by: syzbot <syzbot+721aa903751db87aa244@syzkaller.appspotmail.com> --- kernel/tracepoint.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c index 9f478d29b926..3cfa37a3d05c 100644 --- a/kernel/tracepoint.c +++ b/kernel/tracepoint.c @@ -287,10 +287,8 @@ static int tracepoint_add_func(struct tracepoint *tp, tp_funcs = rcu_dereference_protected(tp->funcs, lockdep_is_held(&tracepoints_mutex)); old = func_add(&tp_funcs, func, prio); - if (IS_ERR(old)) { - WARN_ON_ONCE(PTR_ERR(old) != -ENOMEM); + if (IS_ERR(old)) return PTR_ERR(old); - } /* * rcu_assign_pointer has as smp_store_release() which makes sure @@ -320,7 +318,7 @@ static int tracepoint_remove_func(struct tracepoint *tp, tp_funcs = rcu_dereference_protected(tp->funcs, lockdep_is_held(&tracepoints_mutex)); old = func_remove(&tp_funcs, func); - if (WARN_ON_ONCE(IS_ERR(old))) + if (IS_ERR(old)) return PTR_ERR(old); if (tp_funcs == old) -- 2.18.4
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