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    SubjectRe: [PATCH] bpf: Replace BUG_ON when fp_old is NULL
    On Sun, Dec 15, 2019 at 09:44:32AM -0600, Aditya Pakki wrote:
    > If fp_old is NULL in bpf_prog_realloc, the program does an assertion
    > and crashes. However, we can continue execution by returning NULL to
    > the upper callers. The patch fixes this issue.
    >
    > Signed-off-by: Aditya Pakki <pakki001@umn.edu>
    > ---
    > kernel/bpf/core.c | 3 ++-
    > 1 file changed, 2 insertions(+), 1 deletion(-)
    >
    > diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
    > index 49e32acad7d8..4b46654fb26b 100644
    > --- a/kernel/bpf/core.c
    > +++ b/kernel/bpf/core.c
    > @@ -222,7 +222,8 @@ struct bpf_prog *bpf_prog_realloc(struct bpf_prog *fp_old, unsigned int size,
    > u32 pages, delta;
    > int ret;
    >
    > - BUG_ON(fp_old == NULL);
    > + if (!fp_old)
    > + return NULL;

    This change makes no sense to me. fp_old should be valid. That's the point of
    BUG_ON. It can happen only during development. Can remove BUG_ON just as well
    and let kernel page fault.

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