Commit 6a5abf8c authored by Ilya Leoshkevich's avatar Ilya Leoshkevich Committed by Alexei Starovoitov
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s390/bpf: Fix bpf_arch_text_poke() with new_addr == NULL again 



Commit 7ded842b ("s390/bpf: Fix bpf_plt pointer arithmetic") has
accidentally removed the critical piece of commit c730fce7
("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: 7ded842b ("s390/bpf: Fix bpf_plt pointer arithmetic")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarIlya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/r/20250716194524.48109-2-iii@linux.ibm.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent bf4807c8

arch/s390/net/bpf_jit_comp.c

+9 −1
Original line number Diff line number Diff line
@@ -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;

}



/*