[PATCH AUTOSEL 4.4 26/44] signal: Properly deliver SIGILL from uprobes

[Sasha Levin]

From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>

[ Upstream commit 55a3235fc71bf34303e34a95eeee235b2d2a35dd ]

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

Using SEND_SIG_FORCED for SIGILL 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(SIGILL, SEND_SIG_FORCE, current)
with force_sig(SIG_ILL, current) which gets this right and is
shorter and easier to type.

Fixes: 014940bad8e4 ("uprobes/x86: Send SIGILL if arch_uprobe_post_xol() fails")
Fixes: 0b5256c7f173 ("uprobes: Send SIGILL if handle_trampoline() fails")
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 kernel/events/uprobes.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index aad43c88a6685..8cad3cd92e23e 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1836,7 +1836,7 @@ static void handle_trampoline(struct pt_regs *regs)
 
  sigill:
 	uprobe_warn(current, "handle uretprobe, sending SIGILL.");
-	force_sig_info(SIGILL, SEND_SIG_FORCED, current);
+	force_sig(SIGILL, current);
 
 }
 
@@ -1952,7 +1952,7 @@ static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs)
 
 	if (unlikely(err)) {
 		uprobe_warn(current, "execute the probed insn, sending SIGILL.");
-		force_sig_info(SIGILL, SEND_SIG_FORCED, current);
+		force_sig(SIGILL, current);
 	}
 }
 
-- 
2.20.1