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authorAndy Lutomirski <luto@amacapital.net>2012-10-01 11:40:45 -0700
committerJames Morris <james.l.morris@oracle.com>2012-10-02 21:14:29 +1000
commit87b526d349b04c31d7b3a40b434eb3f825d22305 (patch)
tree2aeec0465901c9623ef7f5b3eb451ea6ccce6ecc /kernel/seccomp.c
parentbf5308344527d015ac9a6d2bda4ad4d40fd7d943 (diff)
downloadlwn-87b526d349b04c31d7b3a40b434eb3f825d22305.tar.gz
lwn-87b526d349b04c31d7b3a40b434eb3f825d22305.zip
seccomp: Make syscall skipping and nr changes more consistent
This fixes two issues that could cause incompatibility between kernel versions: - If a tracer uses SECCOMP_RET_TRACE to select a syscall number higher than the largest known syscall, emulate the unknown vsyscall by returning -ENOSYS. (This is unlikely to make a noticeable difference on x86-64 due to the way the system call entry works.) - On x86-64 with vsyscall=emulate, skipped vsyscalls were buggy. This updates the documentation accordingly. Signed-off-by: Andy Lutomirski <luto@amacapital.net> Acked-by: Will Drewry <wad@chromium.org> Signed-off-by: James Morris <james.l.morris@oracle.com>
Diffstat (limited to 'kernel/seccomp.c')
-rw-r--r--kernel/seccomp.c13
1 files changed, 10 insertions, 3 deletions
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index ee376beedaf9..5af44b593770 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -396,25 +396,29 @@ int __secure_computing(int this_syscall)
#ifdef CONFIG_SECCOMP_FILTER
case SECCOMP_MODE_FILTER: {
int data;
+ struct pt_regs *regs = task_pt_regs(current);
ret = seccomp_run_filters(this_syscall);
data = ret & SECCOMP_RET_DATA;
ret &= SECCOMP_RET_ACTION;
switch (ret) {
case SECCOMP_RET_ERRNO:
/* Set the low-order 16-bits as a errno. */
- syscall_set_return_value(current, task_pt_regs(current),
+ syscall_set_return_value(current, regs,
-data, 0);
goto skip;
case SECCOMP_RET_TRAP:
/* Show the handler the original registers. */
- syscall_rollback(current, task_pt_regs(current));
+ syscall_rollback(current, regs);
/* Let the filter pass back 16 bits of data. */
seccomp_send_sigsys(this_syscall, data);
goto skip;
case SECCOMP_RET_TRACE:
/* Skip these calls if there is no tracer. */
- if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP))
+ if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
+ syscall_set_return_value(current, regs,
+ -ENOSYS, 0);
goto skip;
+ }
/* Allow the BPF to provide the event message */
ptrace_event(PTRACE_EVENT_SECCOMP, data);
/*
@@ -425,6 +429,9 @@ int __secure_computing(int this_syscall)
*/
if (fatal_signal_pending(current))
break;
+ if (syscall_get_nr(current, regs) < 0)
+ goto skip; /* Explicit request to skip. */
+
return 0;
case SECCOMP_RET_ALLOW:
return 0;