From f68b2d5a907b53eed99cf2efcaaae116df73c298 Mon Sep 17 00:00:00 2001 From: Tiwei Bie Date: Tue, 6 Jan 2026 08:12:27 +0800 Subject: [PATCH] um: Preserve errno within signal handler We rely on errno to determine whether a syscall has failed, so we need to ensure that accessing errno is async-signal-safe. Currently, we preserve the errno in sig_handler_common(), but it doesn't cover every possible case. Let's do it in hard_handler() instead, which is the signal handler we actually register. Signed-off-by: Tiwei Bie Link: https://patch.msgid.link/20260106001228.1531146-2-tiwei.btw@antgroup.com Signed-off-by: Johannes Berg --- arch/um/os-Linux/signal.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c index 327fb3c52fc79..de372b936a804 100644 --- a/arch/um/os-Linux/signal.c +++ b/arch/um/os-Linux/signal.c @@ -36,7 +36,6 @@ void (*sig_info[NSIG])(int, struct siginfo *, struct uml_pt_regs *, void *mc) = static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc) { struct uml_pt_regs r; - int save_errno = errno; r.is_user = 0; if (sig == SIGSEGV) { @@ -50,8 +49,6 @@ static void sig_handler_common(int sig, struct siginfo *si, mcontext_t *mc) unblock_signals_trace(); (*sig_info[sig])(sig, si, &r, mc); - - errno = save_errno; } /* @@ -207,8 +204,11 @@ static void hard_handler(int sig, siginfo_t *si, void *p) { ucontext_t *uc = p; mcontext_t *mc = &uc->uc_mcontext; + int save_errno = errno; (*handlers[sig])(sig, (struct siginfo *)si, mc); + + errno = save_errno; } void set_handler(int sig) -- 2.47.3