diff mbox series

bpf, x86: Fix IP after emitting call depth accounting

Message ID 20230107051456.8800-1-joanbrugueram@gmail.com
State New
Headers
Series bpf, x86: Fix IP after emitting call depth accounting |

Commit Message

Joan Bruguera Micó Jan. 7, 2023, 5:14 a.m. UTC 
  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/20230105214922.250473-1-joanbrugueram@gmail.com/
Signed-off-by: Joan Bruguera <joanbrugueram@gmail.com>
---
 arch/x86/net/bpf_jit_comp.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Comments

Joan Bruguera Micó Feb. 28, 2023, 8:47 p.m. UTC | #1 
Friendly ping.

This should fix booting with `retbleed=stuff` on the defaults of various
distros using systemd, e.g. Fedora Rawhide, Arch Linux.

Wrt. Arch Linux, it has picked the patch up,
see https://bugs.archlinux.org/task/77601
diff mbox series

Patch

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index b808be77635e..6e696c6b7018 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -343,9 +343,10 @@  static int emit_call(u8 **pprog, void *func, void *ip)
 
 static int emit_rsb_call(u8 **pprog, void *func, void *ip)
 {
+	void *adjusted_ip;
 	OPTIMIZER_HIDE_VAR(func);
-	x86_call_depth_emit_accounting(pprog, func);
-	return emit_patch(pprog, func, ip, 0xE8);
+	adjusted_ip = (u8 *)ip + x86_call_depth_emit_accounting(pprog, func);
+	return emit_patch(pprog, func, adjusted_ip, 0xE8);
 }
 
 static int emit_jump(u8 **pprog, void *func, void *ip)