Subject: [PATCH RESEND bpf v2 1/2] x86/bpf: Fix IP after emitting call depth accounting

From: Uros Bizjak <[email-masked]>
Date: Mon, 1 Apr 2024 20:55:29 +0200

Adjust the IP passed to `emit_patch` so it calculates the correct offset
for the CALL instruction if `x86_call_depth_emit_accounting` emits code.
Otherwise we will skip some instructions and most likely crash.

Fixes: b2e9dfe54be4 ("x86/bpf: Emit call depth accounting if required")
Link: https://lore.kernel.org/lkml/[email-masked]/
Co-developed-by: Joan Bruguera Micó <[email-masked]>
Signed-off-by: Joan Bruguera Micó <[email-masked]>
Signed-off-by: Uros Bizjak <[email-masked]>
Cc: Alexei Starovoitov <[email-masked]>
Cc: Daniel Borkmann <[email-masked]>
---
v2: Simplify calculation of "ip".
---
 arch/x86/net/bpf_jit_comp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index a7ba8e178645..e55745f512e1 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -480,7 +480,7 @@ static int emit_call(u8 **pprog, void *func, void *ip)
 static int emit_rsb_call(u8 **pprog, void *func, void *ip)
 {
 	OPTIMIZER_HIDE_VAR(func);
-	x86_call_depth_emit_accounting(pprog, func);
+	ip += x86_call_depth_emit_accounting(pprog, func);
 	return emit_patch(pprog, func, ip, 0xE8);
 }
 
-- 
2.42.0