Messages in this thread Patch in this message | | | From | Miles Chen <> | Subject | [PATCH] mm/gup: fix null pointer dereference detected by coverity | Date | Tue, 7 Apr 2020 17:51:07 +0800 |
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In fixup_user_fault(), it is possible that unlocked is NULL, so we should test unlocked before using it.
For example, in arch/arc/kernel/process.c, NULL is passed to fixup_user_fault().
SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new) { ... ret = fixup_user_fault(current, current->mm, (unsigned long) uaddr, FAULT_FLAG_WRITE, NULL); ... }
Fixes: 4a9e1cda2748 ("mm: bring in additional flag for fixup_user_fault to signal unlock") Signed-off-by: Miles Chen <miles.chen@mediatek.com> --- mm/gup.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/gup.c b/mm/gup.c index da3e03185144..a68d11dc232d 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1230,7 +1230,8 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm, if (ret & VM_FAULT_RETRY) { down_read(&mm->mmap_sem); if (!(fault_flags & FAULT_FLAG_TRIED)) { - *unlocked = true; + if (unlocked) + *unlocked = true; fault_flags |= FAULT_FLAG_TRIED; goto retry; } -- 2.18.0 | |