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>
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| @@ -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 | */ | ||
| 343 | static 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: |