Thread (12 messages) 12 messages, 2 authors, 2018-09-08
STALE2819d

[PATCH 03/10] signal: Properly deliver SIGSEGV from x86 uprobes

From: Eric W. Biederman <hidden>
Date: 2018-09-03 20:45:20
Also in: lkml
Subsystem: the rest, uprobes, x86 architecture (32-bit and 64-bit) · Maintainers: Linus Torvalds, Masami Hiramatsu, Oleg Nesterov, Peter Zijlstra, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen

For userspace to tell the difference between an random signal
and an exception, the exception must include siginfo information.

Using SEND_SIG_FORCED for SIGSEGV is thus wrong, and it will result in
userspace seeing si_code == SI_USER (like a random signal) instead of
si_code == SI_KERNEL or a more specific si_code as all exceptions
deliver.

Therefore replace force_sig_info(SIGSEGV, SEND_SIG_FORCE, current)
with force_sig(SIG_SEGV, current) which gets this right and is shorter
and easier to type.

Fixes: 791eca10107f ("uretprobes/x86: Hijack return address")
Signed-off-by: "Eric W. Biederman" <redacted>
---
 arch/x86/kernel/uprobes.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index deb576b23b7c..843feb94a950 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -1086,7 +1086,7 @@ arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs
 		pr_err("return address clobbered: pid=%d, %%sp=%#lx, %%ip=%#lx\n",
 		       current->pid, regs->sp, regs->ip);
 
-		force_sig_info(SIGSEGV, SEND_SIG_FORCED, current);
+		force_sig(SIGSEGV, current);
 	}
 
 	return -1;
-- 
2.17.1
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