On 06/03, Eric Paris wrote:
The audit system previously expected arches calling to audit_syscall_exit to
supply as arguments if the syscall was a success and what the return code was.
Audit also provides a helper AUDITSC_RESULT which was supposed to simplify things
by converting from negative retcodes to an audit internal magic value stating
success or failure. This helper was wrong and could indicate that a valid
pointer returned to userspace was a failed syscall. The fix is to fix the
layering foolishness. We now pass audit_syscall_exit a struct pt_reg and it
in turns calls back into arch code to collect the return value and to
determine if the syscall was a success or failure. We also define a generic
is_syscall_success() macro which determines success/failure based on if the
value is < -MAX_ERRNO. This works for arches like x86 which do not use a
separate mechanism to indicate syscall failure.
I know nothing about audit, but the patch looks fine to me.
But I have a bit off-topic question,
quoted hunk ↗ jump to hunk
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 8a445a0..b7b1f88 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -53,6 +53,7 @@
#include <asm/paravirt.h>
#include <asm/ftrace.h>
#include <asm/percpu.h>
+#include <linux/err.h>
/* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this. */
#include <linux/elf-em.h>
@@ -564,17 +565,16 @@ auditsys:
jmp system_call_fastpath
/*
- * Return fast path for syscall audit. Call audit_syscall_exit()
+ * Return fast path for syscall audit. Call __audit_syscall_exit()
* directly and then jump back to the fast path with TIF_SYSCALL_AUDIT
* masked off.
*/
sysret_audit:
movq RAX-ARGOFFSET(%rsp),%rsi /* second arg, syscall return value */
- cmpq $0,%rsi /* is it < 0? */
- setl %al /* 1 if so, 0 if not */
+ cmpq $-MAX_ERRNO,%rsi /* is it < -MAX_ERRNO? */
+ setbe %al /* 1 if so, 0 if not */
movzbl %al,%edi /* zero-extend that into %edi */
- inc %edi /* first arg, 0->1(AUDITSC_SUCCESS), 1->2(AUDITSC_FAILURE) */
- call audit_syscall_exit
+ call __audit_syscall_exit
With or without this patch, can't we call audit_syscall_exit() twice
if there is something else in _TIF_WORK_SYSCALL_EXIT mask apart from
SYSCALL_AUDIT ? First time it is called from asm, then from
syscall_trace_leave(), no?
For example. The task has TIF_SYSCALL_AUDIT and nothing else, it does
system_call->auditsys->system_call_fastpath. What if it gets, say,
TIF_SYSCALL_TRACE before ret_from_sys_call?
Oleg.