• Frederic Weisbecker's avatar
    ptrace: Prepare to fix racy accesses on task breakpoints · bf26c018
    Frederic Weisbecker authored
    When a task is traced and is in a stopped state, the tracer
    may execute a ptrace request to examine the tracee state and
    get its task struct. Right after, the tracee can be killed
    and thus its breakpoints released.
    This can happen concurrently when the tracer is in the middle
    of reading or modifying these breakpoints, leading to dereferencing
    a freed pointer.
    Hence, to prepare the fix, create a generic breakpoint reference
    holding API. When a reference on the breakpoints of a task is
    held, the breakpoints won't be released until the last reference
    is dropped. After that, no more ptrace request on the task's
    breakpoints can be serviced for the tracer.
    Reported-by: default avatarOleg Nesterov <oleg@redhat.com>
    Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Will Deacon <will.deacon@arm.com>
    Cc: Prasad <prasad@linux.vnet.ibm.com>
    Cc: Paul Mundt <lethal@linux-sh.org>
    Cc: v2.6.33.. <stable@kernel.org>
    Link: http://lkml.kernel.org/r/1302284067-7860-2-git-send-email-fweisbec@gmail.com
sched.h 76 KB