summaryrefslogtreecommitdiffstats
path: root/kernel/signal.c
diff options
context:
space:
mode:
authorThomas Gleixner <tglx@linutronix.de>2021-10-21 15:55:05 -0700
committerBorislav Petkov <bp@suse.de>2021-10-26 10:15:12 +0200
commit1bdda24c4af64cd2d65dec5192ab624c5fee7ca0 (patch)
tree9e96250b0947c570a206842a035ad9f79ad0e45e /kernel/signal.c
parent582b01b6ab2714a0a4d554cea7f0d4efeaa2154d (diff)
downloadlinux-1bdda24c4af64cd2d65dec5192ab624c5fee7ca0.tar.bz2
signal: Add an optional check for altstack size
New x86 FPU features will be very large, requiring ~10k of stack in signal handlers. These new features require a new approach called "dynamic features". The kernel currently tries to ensure that altstacks are reasonably sized. Right now, on x86, sys_sigaltstack() requires a size of >=2k. However, that 2k is a constant. Simply raising that 2k requirement to >10k for the new features would break existing apps which have a compiled-in size of 2k. Instead of universally enforcing a larger stack, prohibit a process from using dynamic features without properly-sized altstacks. This must be enforced in two places: * A dynamic feature can not be enabled without an large-enough altstack for each process thread. * Once a dynamic feature is enabled, any request to install a too-small altstack will be rejected The dynamic feature enabling code must examine each thread in a process to ensure that the altstacks are large enough. Add a new lock (sigaltstack_lock()) to ensure that threads can not race and change their altstack after being examined. Add the infrastructure in form of a config option and provide empty stubs for architectures which do not need dynamic altstack size checks. This implementation will be fleshed out for x86 in a future patch called x86/arch_prctl: Add controls for dynamic XSTATE components [dhansen: commit message. ] Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20211021225527.10184-2-chang.seok.bae@intel.com
Diffstat (limited to 'kernel/signal.c')
-rw-r--r--kernel/signal.c35
1 files changed, 29 insertions, 6 deletions
diff --git a/kernel/signal.c b/kernel/signal.c
index 952741f6d0f9..9278f5291ed6 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -4151,11 +4151,29 @@ int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
return 0;
}
+#ifdef CONFIG_DYNAMIC_SIGFRAME
+static inline void sigaltstack_lock(void)
+ __acquires(&current->sighand->siglock)
+{
+ spin_lock_irq(&current->sighand->siglock);
+}
+
+static inline void sigaltstack_unlock(void)
+ __releases(&current->sighand->siglock)
+{
+ spin_unlock_irq(&current->sighand->siglock);
+}
+#else
+static inline void sigaltstack_lock(void) { }
+static inline void sigaltstack_unlock(void) { }
+#endif
+
static int
do_sigaltstack (const stack_t *ss, stack_t *oss, unsigned long sp,
size_t min_ss_size)
{
struct task_struct *t = current;
+ int ret = 0;
if (oss) {
memset(oss, 0, sizeof(stack_t));
@@ -4179,19 +4197,24 @@ do_sigaltstack (const stack_t *ss, stack_t *oss, unsigned long sp,
ss_mode != 0))
return -EINVAL;
+ sigaltstack_lock();
if (ss_mode == SS_DISABLE) {
ss_size = 0;
ss_sp = NULL;
} else {
if (unlikely(ss_size < min_ss_size))
- return -ENOMEM;
+ ret = -ENOMEM;
+ if (!sigaltstack_size_valid(ss_size))
+ ret = -ENOMEM;
}
-
- t->sas_ss_sp = (unsigned long) ss_sp;
- t->sas_ss_size = ss_size;
- t->sas_ss_flags = ss_flags;
+ if (!ret) {
+ t->sas_ss_sp = (unsigned long) ss_sp;
+ t->sas_ss_size = ss_size;
+ t->sas_ss_flags = ss_flags;
+ }
+ sigaltstack_unlock();
}
- return 0;
+ return ret;
}
SYSCALL_DEFINE2(sigaltstack,const stack_t __user *,uss, stack_t __user *,uoss)