This is a note to let you know that I've just added the patch titled
bpf: Fix extable fixup offset.
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bpf-fix-extable-fixup-offset.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit d9abd0eb941ae411b92c3e8a42d90402a09ff249
Author: Alexei Starovoitov <ast@xxxxxxxxxx>
Date: Wed Dec 15 18:38:30 2021 -0800
bpf: Fix extable fixup offset.
[ Upstream commit 433956e91200734d09958673a56df02d00a917c2 ]
The prog - start_of_ldx is the offset before the faulting ldx to the location
after it, so this will be used to adjust pt_regs->ip for jumping over it and
continuing, and with old temp it would have been fixed up to the wrong offset,
causing crash.
Fixes: 4c5de127598e ("bpf: Emit explicit NULL pointer checks for PROBE_LDX instructions.")
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Reviewed-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 9ea57389c554b..462d8e68b3f43 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1332,7 +1332,7 @@ st: if (is_imm8(insn->off))
* End result: x86 insn "mov rbx, qword ptr [rax+0x14]"
* of 4 bytes will be ignored and rbx will be zero inited.
*/
- ex->fixup = (prog - temp) | (reg2pt_regs[dst_reg] << 8);
+ ex->fixup = (prog - start_of_ldx) | (reg2pt_regs[dst_reg] << 8);
}
break;
