From 07bd18d00d5dcf84eb22f8120f47f09c3d8fe27d Mon Sep 17 00:00:00 2001 From: Will Drewry Date: Thu, 12 Apr 2012 16:47:55 -0500 Subject: asm/syscall.h: add syscall_get_arch Adds a stub for a function that will return the AUDIT_ARCH_* value appropriate to the supplied task based on the system call convention. For audit's use, the value can generally be hard-coded at the audit-site. However, for other functionality not inlined into syscall entry/exit, this makes that information available. seccomp_filter is the first planned consumer and, as such, the comment indicates a tie to CONFIG_HAVE_ARCH_SECCOMP_FILTER. Suggested-by: Roland McGrath Signed-off-by: Will Drewry Acked-by: Serge Hallyn Acked-by: Eric Paris v18: comment and change reword and rebase. v14: rebase/nochanges v13: rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc v12: rebase on to linux-next v11: fixed improper return type v10: introduced Signed-off-by: James Morris --- include/asm-generic/syscall.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'include/asm-generic') diff --git a/include/asm-generic/syscall.h b/include/asm-generic/syscall.h index 5c122ae6bfa6..5b09392db673 100644 --- a/include/asm-generic/syscall.h +++ b/include/asm-generic/syscall.h @@ -142,4 +142,18 @@ void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs, unsigned int i, unsigned int n, const unsigned long *args); +/** + * syscall_get_arch - return the AUDIT_ARCH for the current system call + * @task: task of interest, must be in system call entry tracing + * @regs: task_pt_regs() of @task + * + * Returns the AUDIT_ARCH_* based on the system call convention in use. + * + * It's only valid to call this when @task is stopped on entry to a system + * call, due to %TIF_SYSCALL_TRACE, %TIF_SYSCALL_AUDIT, or %TIF_SECCOMP. + * + * Architectures which permit CONFIG_HAVE_ARCH_SECCOMP_FILTER must + * provide an implementation of this. + */ +int syscall_get_arch(struct task_struct *task, struct pt_regs *regs); #endif /* _ASM_SYSCALL_H */ -- cgit v1.2.3 From a0727e8ce513fe6890416da960181ceb10fbfae6 Mon Sep 17 00:00:00 2001 From: Will Drewry Date: Thu, 12 Apr 2012 16:48:00 -0500 Subject: signal, x86: add SIGSYS info and make it synchronous. This change enables SIGSYS, defines _sigfields._sigsys, and adds x86 (compat) arch support. _sigsys defines fields which allow a signal handler to receive the triggering system call number, the relevant AUDIT_ARCH_* value for that number, and the address of the callsite. SIGSYS is added to the SYNCHRONOUS_MASK because it is desirable for it to have setup_frame() called for it. The goal is to ensure that ucontext_t reflects the machine state from the time-of-syscall and not from another signal handler. The first consumer of SIGSYS would be seccomp filter. In particular, a filter program could specify a new return value, SECCOMP_RET_TRAP, which would result in the system call being denied and the calling thread signaled. This also means that implementing arch-specific support can be dependent upon HAVE_ARCH_SECCOMP_FILTER. Suggested-by: H. Peter Anvin Signed-off-by: Will Drewry Acked-by: Serge Hallyn Reviewed-by: H. Peter Anvin Acked-by: Eric Paris v18: - added acked by, rebase v17: - rebase and reviewed-by addition v14: - rebase/nochanges v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc v12: - reworded changelog (oleg@redhat.com) v11: - fix dropped words in the change description - added fallback copy_siginfo support. - added __ARCH_SIGSYS define to allow stepped arch support. v10: - first version based on suggestion Signed-off-by: James Morris --- arch/x86/ia32/ia32_signal.c | 4 ++++ arch/x86/include/asm/ia32.h | 6 ++++++ include/asm-generic/siginfo.h | 22 ++++++++++++++++++++++ kernel/signal.c | 9 ++++++++- 4 files changed, 40 insertions(+), 1 deletion(-) (limited to 'include/asm-generic') diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c index a69245ba27e3..0b3f2354f6aa 100644 --- a/arch/x86/ia32/ia32_signal.c +++ b/arch/x86/ia32/ia32_signal.c @@ -67,6 +67,10 @@ int copy_siginfo_to_user32(compat_siginfo_t __user *to, siginfo_t *from) switch (from->si_code >> 16) { case __SI_FAULT >> 16: break; + case __SI_SYS >> 16: + put_user_ex(from->si_syscall, &to->si_syscall); + put_user_ex(from->si_arch, &to->si_arch); + break; case __SI_CHLD >> 16: if (ia32) { put_user_ex(from->si_utime, &to->si_utime); diff --git a/arch/x86/include/asm/ia32.h b/arch/x86/include/asm/ia32.h index ee52760549f0..b04cbdb138cd 100644 --- a/arch/x86/include/asm/ia32.h +++ b/arch/x86/include/asm/ia32.h @@ -144,6 +144,12 @@ typedef struct compat_siginfo { int _band; /* POLL_IN, POLL_OUT, POLL_MSG */ int _fd; } _sigpoll; + + struct { + unsigned int _call_addr; /* calling insn */ + int _syscall; /* triggering system call number */ + unsigned int _arch; /* AUDIT_ARCH_* of syscall */ + } _sigsys; } _sifields; } compat_siginfo_t; diff --git a/include/asm-generic/siginfo.h b/include/asm-generic/siginfo.h index 0dd4e87f6fba..31306f55eb02 100644 --- a/include/asm-generic/siginfo.h +++ b/include/asm-generic/siginfo.h @@ -90,9 +90,18 @@ typedef struct siginfo { __ARCH_SI_BAND_T _band; /* POLL_IN, POLL_OUT, POLL_MSG */ int _fd; } _sigpoll; + + /* SIGSYS */ + struct { + void __user *_call_addr; /* calling insn */ + int _syscall; /* triggering system call number */ + unsigned int _arch; /* AUDIT_ARCH_* of syscall */ + } _sigsys; } _sifields; } siginfo_t; +/* If the arch shares siginfo, then it has SIGSYS. */ +#define __ARCH_SIGSYS #endif /* @@ -116,6 +125,11 @@ typedef struct siginfo { #define si_addr_lsb _sifields._sigfault._addr_lsb #define si_band _sifields._sigpoll._band #define si_fd _sifields._sigpoll._fd +#ifdef __ARCH_SIGSYS +#define si_call_addr _sifields._sigsys._call_addr +#define si_syscall _sifields._sigsys._syscall +#define si_arch _sifields._sigsys._arch +#endif #ifdef __KERNEL__ #define __SI_MASK 0xffff0000u @@ -126,6 +140,7 @@ typedef struct siginfo { #define __SI_CHLD (4 << 16) #define __SI_RT (5 << 16) #define __SI_MESGQ (6 << 16) +#define __SI_SYS (7 << 16) #define __SI_CODE(T,N) ((T) | ((N) & 0xffff)) #else #define __SI_KILL 0 @@ -135,6 +150,7 @@ typedef struct siginfo { #define __SI_CHLD 0 #define __SI_RT 0 #define __SI_MESGQ 0 +#define __SI_SYS 0 #define __SI_CODE(T,N) (N) #endif @@ -231,6 +247,12 @@ typedef struct siginfo { #define POLL_HUP (__SI_POLL|6) /* device disconnected */ #define NSIGPOLL 6 +/* + * SIGSYS si_codes + */ +#define SYS_SECCOMP (__SI_SYS|1) /* seccomp triggered */ +#define NSIGSYS 1 + /* * sigevent definitions * diff --git a/kernel/signal.c b/kernel/signal.c index 17afcaf582d0..1a006b5d9d9d 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -160,7 +160,7 @@ void recalc_sigpending(void) #define SYNCHRONOUS_MASK \ (sigmask(SIGSEGV) | sigmask(SIGBUS) | sigmask(SIGILL) | \ - sigmask(SIGTRAP) | sigmask(SIGFPE)) + sigmask(SIGTRAP) | sigmask(SIGFPE) | sigmask(SIGSYS)) int next_signal(struct sigpending *pending, sigset_t *mask) { @@ -2706,6 +2706,13 @@ int copy_siginfo_to_user(siginfo_t __user *to, siginfo_t *from) err |= __put_user(from->si_uid, &to->si_uid); err |= __put_user(from->si_ptr, &to->si_ptr); break; +#ifdef __ARCH_SIGSYS + case __SI_SYS: + err |= __put_user(from->si_call_addr, &to->si_call_addr); + err |= __put_user(from->si_syscall, &to->si_syscall); + err |= __put_user(from->si_arch, &to->si_arch); + break; +#endif default: /* this is just in case for now ... */ err |= __put_user(from->si_pid, &to->si_pid); err |= __put_user(from->si_uid, &to->si_uid); -- cgit v1.2.3 From bb6ea4301a1109afdacaee576fedbfcd7152fc86 Mon Sep 17 00:00:00 2001 From: Will Drewry Date: Thu, 12 Apr 2012 16:48:01 -0500 Subject: seccomp: Add SECCOMP_RET_TRAP Adds a new return value to seccomp filters that triggers a SIGSYS to be delivered with the new SYS_SECCOMP si_code. This allows in-process system call emulation, including just specifying an errno or cleanly dumping core, rather than just dying. Suggested-by: Markus Gutschke Suggested-by: Julien Tinnes Signed-off-by: Will Drewry Acked-by: Eric Paris v18: - acked-by, rebase - don't mention secure_computing_int() anymore v15: - use audit_seccomp/skip - pad out error spacing; clean up switch (indan@nul.nu) v14: - n/a v13: - rebase on to 88ebdda6159ffc15699f204c33feb3e431bf9bdc v12: - rebase on to linux-next v11: - clarify the comment (indan@nul.nu) - s/sigtrap/sigsys v10: - use SIGSYS, syscall_get_arch, updates arch/Kconfig note suggested-by (though original suggestion had other behaviors) v9: - changes to SIGILL v8: - clean up based on changes to dependent patches v7: - introduction Signed-off-by: James Morris --- arch/Kconfig | 14 +++++++++----- include/asm-generic/siginfo.h | 2 +- include/linux/seccomp.h | 1 + kernel/seccomp.c | 26 ++++++++++++++++++++++++++ 4 files changed, 37 insertions(+), 6 deletions(-) (limited to 'include/asm-generic') diff --git a/arch/Kconfig b/arch/Kconfig index beaab68c13b7..66aef13f6038 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -219,11 +219,15 @@ config ARCH_WANT_OLD_COMPAT_IPC config HAVE_ARCH_SECCOMP_FILTER bool help - This symbol should be selected by an architecure if it provides - asm/syscall.h, specifically syscall_get_arguments(), - syscall_get_arch(), and syscall_set_return_value(). Additionally, - its system call entry path must respect a return value of -1 from - __secure_computing() and/or secure_computing(). + This symbol should be selected by an architecure if it provides: + asm/syscall.h: + - syscall_get_arch() + - syscall_get_arguments() + - syscall_rollback() + - syscall_set_return_value() + SIGSYS siginfo_t support must be implemented. + __secure_computing()/secure_computing()'s return value must be + checked, with -1 resulting in the syscall being skipped. config SECCOMP_FILTER def_bool y diff --git a/include/asm-generic/siginfo.h b/include/asm-generic/siginfo.h index 31306f55eb02..af5d0350f84c 100644 --- a/include/asm-generic/siginfo.h +++ b/include/asm-generic/siginfo.h @@ -93,7 +93,7 @@ typedef struct siginfo { /* SIGSYS */ struct { - void __user *_call_addr; /* calling insn */ + void __user *_call_addr; /* calling user insn */ int _syscall; /* triggering system call number */ unsigned int _arch; /* AUDIT_ARCH_* of syscall */ } _sigsys; diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h index b4ce2c816e06..317ccb78cf40 100644 --- a/include/linux/seccomp.h +++ b/include/linux/seccomp.h @@ -19,6 +19,7 @@ * selects the least permissive choice. */ #define SECCOMP_RET_KILL 0x00000000U /* kill the task immediately */ +#define SECCOMP_RET_TRAP 0x00030000U /* disallow and force a SIGSYS */ #define SECCOMP_RET_ERRNO 0x00050000U /* returns an errno */ #define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */ diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 5f78fb6d2212..9c3830692a08 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -332,6 +332,26 @@ void put_seccomp_filter(struct task_struct *tsk) kfree(freeme); } } + +/** + * seccomp_send_sigsys - signals the task to allow in-process syscall emulation + * @syscall: syscall number to send to userland + * @reason: filter-supplied reason code to send to userland (via si_errno) + * + * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info. + */ +static void seccomp_send_sigsys(int syscall, int reason) +{ + struct siginfo info; + memset(&info, 0, sizeof(info)); + info.si_signo = SIGSYS; + info.si_code = SYS_SECCOMP; + info.si_call_addr = (void __user *)KSTK_EIP(current); + info.si_errno = reason; + info.si_arch = syscall_get_arch(current, task_pt_regs(current)); + info.si_syscall = syscall; + force_sig_info(SIGSYS, &info, current); +} #endif /* CONFIG_SECCOMP_FILTER */ /* @@ -382,6 +402,12 @@ int __secure_computing(int this_syscall) syscall_set_return_value(current, task_pt_regs(current), -data, 0); goto skip; + case SECCOMP_RET_TRAP: + /* Show the handler the original registers. */ + syscall_rollback(current, task_pt_regs(current)); + /* Let the filter pass back 16 bits of data. */ + seccomp_send_sigsys(this_syscall, data); + goto skip; case SECCOMP_RET_ALLOW: return 0; case SECCOMP_RET_KILL: -- cgit v1.2.3