[PATCH] i386: seccomp fix for auditing/ptrace (4c7fc722) · Commits · 戴 / test

This is the same issue as ppc64 before, when returning to userland we shouldn't re-compute the seccomp check or the task could be killed during sigreturn when orig_eax is overwritten by the sigreturn syscall. This was found by Roland. This was harmless from a security standpoint, but some i686 users reported failures with auditing enabled system wide (some distro surprisingly makes it the default) and I reproduced it too by keeping the whole workload under strace -f. Patch is tested and works for me under strace -f. nobody@athlon:~/cpushare> strace -o /tmp/o -f python seccomp_test.py make: Nothing to be done for `seccomp_test'. Starting computing some malicious bytecode init load start stop receive_data failure kill exit_code 0 signal 9 The malicious bytecode has been killed successfully by seccomp Starting computing some safe bytecode init load start stop 174 counts kill exit_code 0 signal 0 The seccomp_test.py completed successfully, thank you for testing. (akpm: collaterally cleaned up a bit of do_syscall_trace() too) Signed-off-by:

Andrea Arcangeli <andrea@cpushare.com> Signed-off-by:

Andrew Morton <akpm@osdl.org> Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/ptrace.c

+14 −8

Original line number	Diff line number	Diff line
		@@ -694,17 +694,22 @@ void send_sigtrap(struct task_struct tsk, struct pt_regs regs, int error_code)
		__attribute__((regparm(3)))
		int do_syscall_trace(struct pt_regs *regs, int entryexit)
		{
		int is_sysemu = test_thread_flag(TIF_SYSCALL_EMU), ret = 0;
		/* With TIF_SYSCALL_EMU set we want to ignore TIF_SINGLESTEP for syscall
		* interception. */
		int is_sysemu = test_thread_flag(TIF_SYSCALL_EMU);
		/*
		* With TIF_SYSCALL_EMU set we want to ignore TIF_SINGLESTEP for syscall
		* interception
		*/
		int is_singlestep = !is_sysemu && test_thread_flag(TIF_SINGLESTEP);
		int ret = 0;

		/* do the secure computing check first */
		if (!entryexit)
		secure_computing(regs->orig_eax);

		if (unlikely(current->audit_context)) {
		if (entryexit)
		audit_syscall_exit(current, AUDITSC_RESULT(regs->eax), regs->eax);
		audit_syscall_exit(current, AUDITSC_RESULT(regs->eax),
		regs->eax);
		/* Debug traps, when using PTRACE_SINGLESTEP, must be sent only
		* on the syscall exit path. Normally, when TIF_SYSCALL_AUDIT is
		* not used, entry.S will call us only on syscall exit, not
		@@ -759,6 +764,7 @@ int do_syscall_trace(struct pt_regs *regs, int entryexit)

		regs->orig_eax = -1; /* force skip of syscall restarting */
		if (unlikely(current->audit_context))
		audit_syscall_exit(current, AUDITSC_RESULT(regs->eax), regs->eax);
		audit_syscall_exit(current, AUDITSC_RESULT(regs->eax),
		regs->eax);
		return 1;
		}

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