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Commit ab1c23c2 authored by Bodo Stroesser's avatar Bodo Stroesser Committed by Linus Torvalds
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[PATCH] SYSEMU: fix sysaudit / singlestep interaction 



      Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>

This is simply an adjustment for "Ptrace - i386: fix Syscall Audit interaction
with singlestep" to work on top of SYSEMU patches, too.  On this patch, I have
some doubts: I wonder why we need to alter that way ptrace_disable().

I left the patch this way because it has been extensively tested, but I don't
understand the reason.

The current PTRACE_DETACH handling simply clears child->ptrace; actually this
is not enough because entry.S just looks at the thread_flags; actually,
do_syscall_trace checks current->ptrace but I don't think depending on that is
good, at least for performance, so I think the clearing is done elsewhere.
For instance, on PTRACE_CONT it's done, but doing PTRACE_DETACH without
PTRACE_CONT is possible (and happens when gdb crashes and one kills it
manually).

Signed-off-by: default avatarPaolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
CC: Roland McGrath <roland@redhat.com>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 1b38f006

arch/i386/kernel/ptrace.c

+20 −3
Original line number Diff line number Diff line
@@ -271,6 +271,8 @@ static void clear_singlestep(struct task_struct *child) 
void ptrace_disable(struct task_struct *child)

{ 

	clear_singlestep(child);

	clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);

	clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);

}



/*
@@ -693,14 +695,29 @@ __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 */

	/* With TIF_SYSCALL_EMU set we want to ignore TIF_SINGLESTEP for syscall

	 * interception. */

	int is_singlestep = !is_sysemu && test_thread_flag(TIF_SINGLESTEP);



	/* do the secure computing check first */

	secure_computing(regs->orig_eax);



	if (unlikely(current->audit_context) && entryexit)

	if (unlikely(current->audit_context)) {

		if (entryexit)

			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

		 * entry; so when TIF_SYSCALL_AUDIT is used we must avoid

		 * calling send_sigtrap() on syscall entry.

		 *

		 * Note that when PTRACE_SYSEMU_SINGLESTEP is used,

		 * is_singlestep is false, despite his name, so we will still do

		 * the correct thing.

		 */

		else if (is_singlestep)

			goto out;

	}



	if (!(current->ptrace & PT_PTRACED))

		goto out;