Messages in this thread Patch in this message | | | From | "Chang S. Bae" <> | Subject | [PATCH 01/23] signal: Add an optional check for altstack size | Date | Thu, 21 Oct 2021 15:55:05 -0700 |
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From: Thomas Gleixner <tglx@linutronix.de>
The upcoming support for dynamically enabled FPU features on x86 requires an architecture specific sanity check and serialization of the store to task::sas_ss_size. The check is required to ensure that:
- Enabling of a dynamic feature, which changes the sigframe size fits into an enabled sigaltstack
- Installing a too small sigaltstack after a dynamic feature has been added is not possible.
It needs serialization to prevent race conditions of all sorts in the feature enable code as that has to walk the thread list of the process.
Add the infrastructure in form of a config option and provide empty stubs for architectures which do not need that.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> Cc: Oleg Nesterov <ole@redhat.com> Cc: Eric W. Biederman <ebiederm@xmission.com> --- arch/Kconfig | 3 +++ include/linux/signal.h | 6 ++++++ kernel/signal.c | 35 +++++++++++++++++++++++++++++------ 3 files changed, 38 insertions(+), 6 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig index 8df1c7102643..af5cf3009b4f 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -1288,6 +1288,9 @@ config ARCH_HAS_ELFCORE_COMPAT config ARCH_HAS_PARANOID_L1D_FLUSH bool +config DYNAMIC_SIGFRAME + bool + source "kernel/gcov/Kconfig" source "scripts/gcc-plugins/Kconfig" diff --git a/include/linux/signal.h b/include/linux/signal.h index 3f96a6374e4f..7d34105e20c6 100644 --- a/include/linux/signal.h +++ b/include/linux/signal.h @@ -464,6 +464,12 @@ int __save_altstack(stack_t __user *, unsigned long); unsafe_put_user(t->sas_ss_size, &__uss->ss_size, label); \ } while (0); +#ifdef CONFIG_DYNAMIC_SIGFRAME +bool sigaltstack_size_valid(size_t ss_size); +#else +static inline bool sigaltstack_size_valid(size_t size) { return true; } +#endif /* !CONFIG_DYNAMIC_SIGFRAME */ + #ifdef CONFIG_PROC_FS struct seq_file; extern void render_sigset_t(struct seq_file *, const char *, sigset_t *); 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(¤t->sighand->siglock) +{ + spin_lock_irq(¤t->sighand->siglock); +} + +static inline void sigaltstack_unlock(void) + __releases(¤t->sighand->siglock) +{ + spin_unlock_irq(¤t->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) -- 2.17.1
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