From: Andrei Vagin avagin@gmail.com
[ Upstream commit fcfc2aa0185f4a731d05a21e9f359968fdfd02e7 ]
There are a few system calls (pselect, ppoll, etc) which replace a task sigmask while they are running in a kernel-space
When a task calls one of these syscalls, the kernel saves a current sigmask in task->saved_sigmask and sets a syscall sigmask.
On syscall-exit-stop, ptrace traps a task before restoring the saved_sigmask, so PTRACE_GETSIGMASK returns the syscall sigmask and PTRACE_SETSIGMASK does nothing, because its sigmask is replaced by saved_sigmask, when the task returns to user-space.
This patch fixes this problem. PTRACE_GETSIGMASK returns saved_sigmask if it's set. PTRACE_SETSIGMASK drops the TIF_RESTORE_SIGMASK flag.
Link: http://lkml.kernel.org/r/20181120060616.6043-1-avagin@gmail.com Fixes: 29000caecbe8 ("ptrace: add ability to get/set signal-blocked mask") Signed-off-by: Andrei Vagin avagin@gmail.com Acked-by: Oleg Nesterov oleg@redhat.com Cc: "Eric W. Biederman" ebiederm@xmission.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin (Microsoft) sashal@kernel.org --- include/linux/sched/signal.h | 18 ++++++++++++++++++ kernel/ptrace.c | 15 +++++++++++++-- 2 files changed, 31 insertions(+), 2 deletions(-)
diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h index fbf86ecd149d..bcaba7e8ca6e 100644 --- a/include/linux/sched/signal.h +++ b/include/linux/sched/signal.h @@ -377,10 +377,20 @@ static inline void set_restore_sigmask(void) set_thread_flag(TIF_RESTORE_SIGMASK); WARN_ON(!test_thread_flag(TIF_SIGPENDING)); } + +static inline void clear_tsk_restore_sigmask(struct task_struct *tsk) +{ + clear_tsk_thread_flag(tsk, TIF_RESTORE_SIGMASK); +} + static inline void clear_restore_sigmask(void) { clear_thread_flag(TIF_RESTORE_SIGMASK); } +static inline bool test_tsk_restore_sigmask(struct task_struct *tsk) +{ + return test_tsk_thread_flag(tsk, TIF_RESTORE_SIGMASK); +} static inline bool test_restore_sigmask(void) { return test_thread_flag(TIF_RESTORE_SIGMASK); @@ -398,6 +408,10 @@ static inline void set_restore_sigmask(void) current->restore_sigmask = true; WARN_ON(!test_thread_flag(TIF_SIGPENDING)); } +static inline void clear_tsk_restore_sigmask(struct task_struct *tsk) +{ + tsk->restore_sigmask = false; +} static inline void clear_restore_sigmask(void) { current->restore_sigmask = false; @@ -406,6 +420,10 @@ static inline bool test_restore_sigmask(void) { return current->restore_sigmask; } +static inline bool test_tsk_restore_sigmask(struct task_struct *tsk) +{ + return tsk->restore_sigmask; +} static inline bool test_and_clear_restore_sigmask(void) { if (!current->restore_sigmask) diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 84b1367935e4..f1c85b6c39ae 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -29,6 +29,7 @@ #include <linux/hw_breakpoint.h> #include <linux/cn_proc.h> #include <linux/compat.h> +#include <linux/sched/signal.h>
/* * Access another process' address space via ptrace. @@ -925,18 +926,26 @@ int ptrace_request(struct task_struct *child, long request, ret = ptrace_setsiginfo(child, &siginfo); break;
- case PTRACE_GETSIGMASK: + case PTRACE_GETSIGMASK: { + sigset_t *mask; + if (addr != sizeof(sigset_t)) { ret = -EINVAL; break; }
- if (copy_to_user(datavp, &child->blocked, sizeof(sigset_t))) + if (test_tsk_restore_sigmask(child)) + mask = &child->saved_sigmask; + else + mask = &child->blocked; + + if (copy_to_user(datavp, mask, sizeof(sigset_t))) ret = -EFAULT; else ret = 0;
break; + }
case PTRACE_SETSIGMASK: { sigset_t new_set; @@ -962,6 +971,8 @@ int ptrace_request(struct task_struct *child, long request, child->blocked = new_set; spin_unlock_irq(&child->sighand->siglock);
+ clear_tsk_restore_sigmask(child); + ret = 0; break; }