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authorAlexei Starovoitov <ast@kernel.org>2019-02-10 12:52:35 -0800
committerDaniel Borkmann <daniel@iogearbox.net>2019-02-11 16:36:24 +0100
commit3defaf2f15b2bfd86c6664181ac009e91985f8ac (patch)
treee14f5b1fb6e2fb4447518ad12b7ef38618e8f5a1 /kernel
parente6762c8bcf982821935a2b1cb33cf8335d0eefae (diff)
bpf: fix lockdep false positive in stackmap
Lockdep warns about false positive: [ 11.211460] ------------[ cut here ]------------ [ 11.211936] DEBUG_LOCKS_WARN_ON(depth <= 0) [ 11.211985] WARNING: CPU: 0 PID: 141 at ../kernel/locking/lockdep.c:3592 lock_release+0x1ad/0x280 [ 11.213134] Modules linked in: [ 11.214954] RIP: 0010:lock_release+0x1ad/0x280 [ 11.223508] Call Trace: [ 11.223705] <IRQ> [ 11.223874] ? __local_bh_enable+0x7a/0x80 [ 11.224199] up_read+0x1c/0xa0 [ 11.224446] do_up_read+0x12/0x20 [ 11.224713] irq_work_run_list+0x43/0x70 [ 11.225030] irq_work_run+0x26/0x50 [ 11.225310] smp_irq_work_interrupt+0x57/0x1f0 [ 11.225662] irq_work_interrupt+0xf/0x20 since rw_semaphore is released in a different task vs task that locked the sema. It is expected behavior. Fix the warning with up_read_non_owner() and rwsem_release() annotation. Fixes: bae77c5eb5b2 ("bpf: enable stackmap with build_id in nmi context") Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/stackmap.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index d43b14535827..950ab2f28922 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -44,7 +44,7 @@ static void do_up_read(struct irq_work *entry)
struct stack_map_irq_work *work;
work = container_of(entry, struct stack_map_irq_work, irq_work);
- up_read(work->sem);
+ up_read_non_owner(work->sem);
work->sem = NULL;
}
@@ -338,6 +338,12 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
} else {
work->sem = &current->mm->mmap_sem;
irq_work_queue(&work->irq_work);
+ /*
+ * The irq_work will release the mmap_sem with
+ * up_read_non_owner(). The rwsem_release() is called
+ * here to release the lock from lockdep's perspective.
+ */
+ rwsem_release(&current->mm->mmap_sem.dep_map, 1, _RET_IP_);
}
}