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author | Song Liu <song@kernel.org> | 2023-10-12 08:57:41 +0300 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-11-20 13:59:03 +0300 |
commit | 6e6dffbb72d4a281d15a7f7a58f5b9f7c2cb09a2 (patch) | |
tree | 52d0767ba02de5312ddd6b10ce8a1ba36414d69f /net/mptcp | |
parent | d4b8c082f620690f798b36da8afe3e21c45fdce4 (diff) | |
download | linux-6e6dffbb72d4a281d15a7f7a58f5b9f7c2cb09a2.tar.xz |
bpf: Fix unnecessary -EBUSY from htab_lock_bucket
[ Upstream commit d35381aa73f7e1e8b25f3ed5283287a64d9ddff5 ]
htab_lock_bucket uses the following logic to avoid recursion:
1. preempt_disable();
2. check percpu counter htab->map_locked[hash] for recursion;
2.1. if map_lock[hash] is already taken, return -BUSY;
3. raw_spin_lock_irqsave();
However, if an IRQ hits between 2 and 3, BPF programs attached to the IRQ
logic will not able to access the same hash of the hashtab and get -EBUSY.
This -EBUSY is not really necessary. Fix it by disabling IRQ before
checking map_locked:
1. preempt_disable();
2. local_irq_save();
3. check percpu counter htab->map_locked[hash] for recursion;
3.1. if map_lock[hash] is already taken, return -BUSY;
4. raw_spin_lock().
Similarly, use raw_spin_unlock() and local_irq_restore() in
htab_unlock_bucket().
Fixes: 20b6cc34ea74 ("bpf: Avoid hashtab deadlock with map_locked")
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/7a9576222aa40b1c84ad3a9ba3e64011d1a04d41.camel@linux.ibm.com
Link: https://lore.kernel.org/bpf/20231012055741.3375999-1-song@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'net/mptcp')
0 files changed, 0 insertions, 0 deletions