[PATCH v10 08/11] seccomp: Add SECCOMP_RET_TRAP
From: Will Drewry <wad@chromium.org>
Date: 2012-02-21 17:33:04
Also in:
lkml, netdev
Subsystem:
secure computing, the rest · Maintainers:
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.
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/linux/seccomp.h | 1 +
kernel/seccomp.c | 28 ++++++++++++++++++++++++++++
3 files changed, 38 insertions(+), 5 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index aa00571..6d6d9dc 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig@@ -202,11 +202,15 @@ config HAVE_CMPXCHG_DOUBLE 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/linux/seccomp.h b/include/linux/seccomp.h
index 54ecb61..d039b7b 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 send sigtrap */ #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 23f1844..fc25d3a 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c@@ -279,6 +279,26 @@ void copy_seccomp(struct seccomp *child, child->mode = prev->mode; child->filter = get_seccomp_filter(prev->filter); } + +/** + * 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 */ /*
@@ -332,6 +352,14 @@ 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