[PATCH v12 09/13] seccomp: Add SECCOMP_RET_TRAP
From: Will Drewry <wad@chromium.org>
Date: 2012-02-29 23:56:43
Also in:
linux-arch, lkml
Subsystem:
generic include/asm header files, secure computing, the rest · Maintainers:
Arnd Bergmann, Kees Cook, Linus Torvalds
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.
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
Suggested-by: Markus Gutschke <redacted>
Suggested-by: Julien Tinnes <redacted>
Signed-off-by: Will Drewry <wad@chromium.org>
---
arch/Kconfig | 14 +++++++++-----
include/asm-generic/siginfo.h | 2 +-
include/linux/seccomp.h | 1 +
kernel/seccomp.c | 28 ++++++++++++++++++++++++++++
4 files changed, 39 insertions(+), 6 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index 1350d07..6908bf6 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig@@ -236,11 +236,15 @@ 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_int() 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_int()/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 31306f5..af5d035 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 a81fccd..3fe48fd 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 0x00020000U /* disallow and force a SIGSYS */ #define SECCOMP_RET_ERRNO 0x00030000U /* returns an errno */ #define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 88dd568..10c6077 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c@@ -272,6 +272,26 @@ void put_seccomp_filter(struct seccomp_filter *orig) 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 */ /*
@@ -326,6 +346,14 @@ int __secure_computing_int(int this_syscall) -(action & SECCOMP_RET_DATA), 0); return -1; + case SECCOMP_RET_TRAP: { + int reason_code = action & SECCOMP_RET_DATA; + /* 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, reason_code); + return -1; + } case SECCOMP_RET_ALLOW: return 0; case SECCOMP_RET_KILL:
--
1.7.5.4