signal: Properly deliver SIGSEGV from x86 uprobes

[ Upstream commit 4a63c1ff ]

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: 791eca10 ("uretprobes/x86: Hijack return address")
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

arch/x86/kernel/uprobes.c

@@ -1089,7 +1089,7 @@ 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;