mm/kmemleak: avoid deadlock by moving pr_warn() outside kmemleak_lock

When netpoll is enabled, calling pr_warn_once() while holding
kmemleak_lock in mem_pool_alloc() can cause a deadlock due to lock
inversion with the netconsole subsystem.  This occurs because
pr_warn_once() may trigger netpoll, which eventually leads to
__alloc_skb() and back into kmemleak code, attempting to reacquire
kmemleak_lock.

This is the path for the deadlock.

mem_pool_alloc()
  -> raw_spin_lock_irqsave(&kmemleak_lock, flags);
      -> pr_warn_once()
          -> netconsole subsystem
	     -> netpoll
	         -> __alloc_skb
		   -> __create_object
		     -> raw_spin_lock_irqsave(&kmemleak_lock, flags);

Fix this by setting a flag and issuing the pr_warn_once() after
kmemleak_lock is released.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: c5665868183f ("mm: kmemleak: use the memory pool for early allocations")
Signed-off-by: Breno Leitao <[email protected]>
Reported-by: Jakub Kicinski <[email protected]>
Acked-by: Catalin Marinas <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions