From b7dafa0ef3145c31d7753be0a08b3cbda51f0209 Mon Sep 17 00:00:00 2001 From: Jan Kiszka Date: Thu, 10 May 2012 10:04:36 -0300 Subject: [PATCH] compat: Fix RT signal mask corruption via sigprocmask compat_sys_sigprocmask reads a smaller signal mask from userspace than sigprogmask accepts for setting. So the high word of blocked.sig[0] will be cleared, releasing any potentially blocked RT signal. This was discovered via userspace code that relies on get/setcontext. glibc's i386 versions of those functions use sigprogmask instead of rt_sigprogmask to save/restore signal mask and caused RT signal unblocking this way. As suggested by Linus, this replaces the sys_sigprocmask based compat version with one that open-codes the required logic, including the merge of the existing blocked set with the new one provided on SIG_SETMASK. Signed-off-by: Jan Kiszka Signed-off-by: Linus Torvalds --- kernel/compat.c | 63 ++++++++++++++++++++++++++++++++++++------------- 1 file changed, 46 insertions(+), 17 deletions(-) diff --git a/kernel/compat.c b/kernel/compat.c index 74ff8498809a..d2c67aa49ae6 100644 --- a/kernel/compat.c +++ b/kernel/compat.c @@ -372,25 +372,54 @@ asmlinkage long compat_sys_sigpending(compat_old_sigset_t __user *set) #ifdef __ARCH_WANT_SYS_SIGPROCMASK -asmlinkage long compat_sys_sigprocmask(int how, compat_old_sigset_t __user *set, - compat_old_sigset_t __user *oset) +/* + * sys_sigprocmask SIG_SETMASK sets the first (compat) word of the + * blocked set of signals to the supplied signal set + */ +static inline void compat_sig_setmask(sigset_t *blocked, compat_sigset_word set) { - old_sigset_t s; - long ret; - mm_segment_t old_fs; + memcpy(blocked->sig, &set, sizeof(set)); +} - if (set && get_user(s, set)) - return -EFAULT; - old_fs = get_fs(); - set_fs(KERNEL_DS); - ret = sys_sigprocmask(how, - set ? (old_sigset_t __user *) &s : NULL, - oset ? (old_sigset_t __user *) &s : NULL); - set_fs(old_fs); - if (ret == 0) - if (oset) - ret = put_user(s, oset); - return ret; +asmlinkage long compat_sys_sigprocmask(int how, + compat_old_sigset_t __user *nset, + compat_old_sigset_t __user *oset) +{ + old_sigset_t old_set, new_set; + sigset_t new_blocked; + + old_set = current->blocked.sig[0]; + + if (nset) { + if (get_user(new_set, nset)) + return -EFAULT; + new_set &= ~(sigmask(SIGKILL) | sigmask(SIGSTOP)); + + new_blocked = current->blocked; + + switch (how) { + case SIG_BLOCK: + sigaddsetmask(&new_blocked, new_set); + break; + case SIG_UNBLOCK: + sigdelsetmask(&new_blocked, new_set); + break; + case SIG_SETMASK: + compat_sig_setmask(&new_blocked, new_set); + break; + default: + return -EINVAL; + } + + set_current_blocked(&new_blocked); + } + + if (oset) { + if (put_user(old_set, oset)) + return -EFAULT; + } + + return 0; } #endif -- 2.20.1