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ptrace: kill BKL in ptrace syscall 

The comment suggests that this usage is stale. There is no bkl in the
exec path so if there is a race lurking there, the bkl in ptrace is
not going to help in this regard.

Overview of the possibility of "accidental" races this bkl might
protect:

- ptrace_traceme() is protected against task removal and concurrent
read/write on current->ptrace as it locks write tasklist_lock.

- arch_ptrace_attach() is serialized by ptrace_traceme() against
concurrent PTRACE_TRACEME or PTRACE_ATTACH

- ptrace_attach() is protected the same way ptrace_traceme() and
in turn serializes arch_ptrace_attach()

- ptrace_check_attach() does its own well described serializing too.

There is no obvious race here.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Roland McGrath <roland@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Roland McGrath <roland@redhat.com>
This commit is contained in:
Arnd Bergmann 2010-02-27 19:49:37 +01:00 committed by Frederic Weisbecker
parent 2eaa9cfdf3
commit 5534ecb2dd
1 changed files with 0 additions and 10 deletions
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10
kernel/ptrace.c
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@ -666,10 +666,6 @@ SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data)
struct task_struct *child;
long ret;
/*
* This lock_kernel fixes a subtle race with suid exec
*/
lock_kernel();
if (request == PTRACE_TRACEME) {
ret = ptrace_traceme();
if (!ret)
@ -703,7 +699,6 @@ SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data)
out_put_task_struct:
put_task_struct(child);
out:
unlock_kernel();
return ret;
}
@ -813,10 +808,6 @@ asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
struct task_struct *child;
long ret;
/*
* This lock_kernel fixes a subtle race with suid exec
*/
lock_kernel();
if (request == PTRACE_TRACEME) {
ret = ptrace_traceme();
goto out;
@ -846,7 +837,6 @@ asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
out_put_task_struct:
put_task_struct(child);
out:
unlock_kernel();
return ret;
}
#endif /* CONFIG_COMPAT */