From: Miles Chen <miles.chen@xxxxxxxxxxxx>
Subject: mm/gup: fix null pointer dereference detected by coverity
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);
...
}
Link: http://lkml.kernel.org/r/20200407095107.1988-1-miles.chen@xxxxxxxxxxxx
Fixes: 4a9e1cda2748 ("mm: bring in additional flag for fixup_user_fault to signal unlock")
Signed-off-by: Miles Chen <miles.chen@xxxxxxxxxxxx>
Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/gup.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/mm/gup.c~mm-gup-fix-null-pointer-dereference-detected-by-coverity
+++ a/mm/gup.c
@@ -1231,7 +1231,8 @@ retry:
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;
}
_
