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| author | Andrii Nakryiko <andrii@kernel.org> | 2025-02-25 14:32:14 -0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2025-02-25 23:36:19 +0100 |
| commit | f8c857238a392f21d5726d07966f6061007c8d4f (patch) | |
| tree | 43e19533869aa311aaaa0248a93b6da6b7169c35 /kernel | |
| parent | 68a9b0e313302451468c0b0eda53c383fa51a8f4 (diff) | |
| download | linux-f8c857238a392f21d5726d07966f6061007c8d4f.tar.gz linux-f8c857238a392f21d5726d07966f6061007c8d4f.tar.bz2 linux-f8c857238a392f21d5726d07966f6061007c8d4f.zip | |
uprobes: Remove too strict lockdep_assert() condition in hprobe_expire()
hprobe_expire() is used to atomically switch pending uretprobe instance
(struct return_instance) from being SRCU protected to be refcounted.
This can be done from background timer thread, or synchronously within
current thread when task is forked.
In the former case, return_instance has to be protected through RCU read
lock, and that's what hprobe_expire() used to check with
lockdep_assert(rcu_read_lock_held()).
But in the latter case (hprobe_expire() called from dup_utask()) there
is no RCU lock being held, and it's both unnecessary and incovenient.
Inconvenient due to the intervening memory allocations inside
dup_return_instance()'s loop. Unnecessary because dup_utask() is called
synchronously in current thread, and no uretprobe can run at that point,
so return_instance can't be freed either.
So drop rcu_read_lock_held() condition, and expand corresponding comment
to explain necessary lifetime guarantees. lockdep_assert()-detected
issue is a false positive.
Fixes: dd1a7567784e ("uprobes: SRCU-protect uretprobe lifetime (with timeout)")
Reported-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20250225223214.2970740-1-andrii@kernel.org
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/events/uprobes.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index af53fbd2d12c..b4ca8898fe17 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -767,10 +767,14 @@ static struct uprobe *hprobe_expire(struct hprobe *hprobe, bool get) enum hprobe_state hstate; /* - * return_instance's hprobe is protected by RCU. - * Underlying uprobe is itself protected from reuse by SRCU. + * Caller should guarantee that return_instance is not going to be + * freed from under us. This can be achieved either through holding + * rcu_read_lock() or by owning return_instance in the first place. + * + * Underlying uprobe is itself protected from reuse by SRCU, so ensure + * SRCU lock is held properly. */ - lockdep_assert(rcu_read_lock_held() && srcu_read_lock_held(&uretprobes_srcu)); + lockdep_assert(srcu_read_lock_held(&uretprobes_srcu)); hstate = READ_ONCE(hprobe->state); switch (hstate) { |