Messages in this thread Patch in this message | | | From | Siddhesh Poyarekar <> | Subject | [PATCH] Avoid dereferencing a possibly NULL mm | Date | Sat, 2 Jun 2012 22:24:22 +0530 |
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The NULL check for mm in exit_mm occurs after mm_release is called. This looks wrong because mm_release dereferences mm:
... if (!(tsk->flags & PF_SIGNALED) && atomic_read(&mm->mm_users) > 1) { /* ...
This dereference seems unsafe and hence is fixed by moving the NULL check above mm_release.
Signed-off-by: Siddhesh Poyarekar <siddhesh.poyarekar@gmail.com> --- kernel/exit.c | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-)
diff --git a/kernel/exit.c b/kernel/exit.c index 34867cc..15fe63c 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -640,9 +640,11 @@ static void exit_mm(struct task_struct * tsk) struct mm_struct *mm = tsk->mm; struct core_state *core_state; - mm_release(tsk, mm); if (!mm) return; + + mm_release(tsk, mm); + /* * Serialize with any possible pending coredump. * We must hold mmap_sem around checking core_state -- 1.7.7.6
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