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s390/bpf: Fix bpf_arch_text_poke() with new_addr == NULL again

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Commit 7ded842b35 ("s390/bpf: Fix bpf_plt pointer arithmetic") has
accidentally removed the critical piece of commit c730fce7c7
("s390/bpf: Fix bpf_arch_text_poke() with new_addr == NULL"), causing
intermittent kernel panics in e.g. perf's on_switch() prog to reappear.

Restore the fix and add a comment.

Fixes: 7ded842b35 ("s390/bpf: Fix bpf_plt pointer arithmetic")
Cc: stable@vger.kernel.org
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/r/20250716194524.48109-2-iii@linux.ibm.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Ilya Leoshkevich 2025-07-16 21:35:06 +02:00 committed by Alexei Starovoitov
parent bf4807c89d
commit 6a5abf8cf1
1 changed files with 9 additions and 1 deletions
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10
arch/s390/net/bpf_jit_comp.c
View File

@ -566,7 +566,15 @@ static void bpf_jit_plt(struct bpf_plt *plt, void *ret, void *target)
{
memcpy(plt, &bpf_plt, sizeof(*plt));
plt->ret = ret;
plt->target = target;
/*
* (target == NULL) implies that the branch to this PLT entry was
* patched and became a no-op. However, some CPU could have jumped
* to this PLT entry before patching and may be still executing it.
*
* Since the intention in this case is to make the PLT entry a no-op,
* make the target point to the return label instead of NULL.
*/
plt->target = target ?: ret;
}
/*