bpf: Fix trampoline usage in preempt

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commit 05d57f1793 upstream.

Though the second half of trampoline page is unused a task could be
preempted in the middle of the first half of trampoline and two
updates to trampoline would change the code from underneath the
preempted task. Hence wait for tasks to voluntarily schedule or go
to userspace. Add similar wait before freeing the trampoline.

Fixes: fec56f5890 ("bpf: Introduce BPF trampoline")
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/bpf/20200121032231.3292185-1-ast@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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Alexei Starovoitov 2020-01-20 19:22:31 -08:00 • committed by Greg Kroah-Hartman

parent 24e11a34b0

commit 23912be9da

1 changed files with 10 additions and 0 deletions

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kernel/bpf/trampoline.c

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