[PATCH AUTOSEL 4.14 065/103] signal: Properly deliver SIGILL from uprobes

Sasha Levin
2019-11-08T11:44:55Z

From: "Eric W. Biederman" <ebiederm@xmission.com>

[ 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@linutronix.de>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 01941cffa9c2f..c74fc98262508 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1854,7 +1854,7 @@ 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);

}

@@ -1970,7 +1970,7 @@ 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