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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 <markus@chromium.org> Suggested-by: Julien Tinnes <jln@chromium.org> Signed-off-by: Will Drewry <wad@chromium.org> Acked-by: Eric Paris <eparis@redhat.com>

Will Drewry committed 14 years ago

Commit bb6ea431 parent a0727e84 files · +37 −6Browse files

Unified · Split

4 files
  1. arch/Kconfig +9 −5
  2. include/asm-generic/siginfo.h +1 −1
  3. include/linux/seccomp.h +1 −0
  4. kernel/seccomp.c +26 −0
arch/Kconfig+9−5
@@ -219,11 +219,15 @@ config ARCH_WANT_OLD_COMPAT_IPC · 218 unmodified lines
219config HAVE_ARCH_SECCOMP_FILTER219config HAVE_ARCH_SECCOMP_FILTER
220 bool220 bool
221 help221 help
222 This symbol should be selected by an architecure if it provides222 This symbol should be selected by an architecure if it provides:
223 asm/syscall.h, specifically syscall_get_arguments(),223 asm/syscall.h:
224 syscall_get_arch(), and syscall_set_return_value(). Additionally,224 - syscall_get_arch()
225 its system call entry path must respect a return value of -1 from225 - syscall_get_arguments()
226 __secure_computing() and/or secure_computing().226 - syscall_rollback()
227 - syscall_set_return_value()
228 SIGSYS siginfo_t support must be implemented.
229 __secure_computing()/secure_computing()'s return value must be
230 checked, with -1 resulting in the syscall being skipped.
227 231
228config SECCOMP_FILTER232config SECCOMP_FILTER
229 def_bool y233 def_bool y
include/asm-generic/siginfo.h+1−1
@@ -93,7 +93,7 @@ typedef struct siginfo { · 92 unmodified lines
93 93
94 /* SIGSYS */94 /* SIGSYS */
95 struct {95 struct {
96 void __user *_call_addr; /* calling insn */96 void __user *_call_addr; /* calling user insn */
97 int _syscall; /* triggering system call number */97 int _syscall; /* triggering system call number */
98 unsigned int _arch; /* AUDIT_ARCH_* of syscall */98 unsigned int _arch; /* AUDIT_ARCH_* of syscall */
99 } _sigsys;99 } _sigsys;
include/linux/seccomp.h+1−0
@@ -19,6 +19,7 @@ · 18 unmodified lines
19 * selects the least permissive choice.19 * selects the least permissive choice.
20 */20 */
21#define SECCOMP_RET_KILL 0x00000000U /* kill the task immediately */21#define SECCOMP_RET_KILL 0x00000000U /* kill the task immediately */
22#define SECCOMP_RET_TRAP 0x00030000U /* disallow and force a SIGSYS */
22#define SECCOMP_RET_ERRNO 0x00050000U /* returns an errno */23#define SECCOMP_RET_ERRNO 0x00050000U /* returns an errno */
23#define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */24#define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */
24 25
kernel/seccomp.c+26−0
@@ -332,6 +332,26 @@ void put_seccomp_filter(struct task_struct *tsk) · 331 unmodified lines
332 kfree(freeme);332 kfree(freeme);
333 }333 }
334}334}
335
336/**
337 * seccomp_send_sigsys - signals the task to allow in-process syscall emulation
338 * @syscall: syscall number to send to userland
339 * @reason: filter-supplied reason code to send to userland (via si_errno)
340 *
341 * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info.
342 */
343static void seccomp_send_sigsys(int syscall, int reason)
344{
345 struct siginfo info;
346 memset(&info, 0, sizeof(info));
347 info.si_signo = SIGSYS;
348 info.si_code = SYS_SECCOMP;
349 info.si_call_addr = (void __user *)KSTK_EIP(current);
350 info.si_errno = reason;
351 info.si_arch = syscall_get_arch(current, task_pt_regs(current));
352 info.si_syscall = syscall;
353 force_sig_info(SIGSYS, &info, current);
354}
335#endif /* CONFIG_SECCOMP_FILTER */355#endif /* CONFIG_SECCOMP_FILTER */
336 356
337/*357/*
@@ -382,6 +402,12 @@ int __secure_computing(int this_syscall) · 44 unmodified lines
382 syscall_set_return_value(current, task_pt_regs(current),402 syscall_set_return_value(current, task_pt_regs(current),
383 -data, 0);403 -data, 0);
384 goto skip;404 goto skip;
405 case SECCOMP_RET_TRAP:
406 /* Show the handler the original registers. */
407 syscall_rollback(current, task_pt_regs(current));
408 /* Let the filter pass back 16 bits of data. */
409 seccomp_send_sigsys(this_syscall, data);
410 goto skip;
385 case SECCOMP_RET_ALLOW:411 case SECCOMP_RET_ALLOW:
386 return 0;412 return 0;
387 case SECCOMP_RET_KILL:413 case SECCOMP_RET_KILL: