[PATCH 1/4] ipc, shm: guard against non-existant vma in shmdt(2)

[Davidlohr Bueso]

When !CONFIG_MMU there's a chance we can derefence a NULL pointer
when the VM area isn't found - check the return value of find_vma().

Also, remove the redundant -EINVAL return: retval is set to the proper
return code and *only* changed to 0, when we actually unmap the segments.

Signed-off-by: Davidlohr Bueso <davidlohr.bueso@xxxxxx>
---
 ipc/shm.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/ipc/shm.c b/ipc/shm.c
index 59f2194..c7ee2f6 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -1288,8 +1288,7 @@ SYSCALL_DEFINE1(shmdt, char __user *, shmaddr)
 #else /* CONFIG_MMU */
 	/* under NOMMU conditions, the exact address to be destroyed must be
 	 * given */
-	retval = -EINVAL;
-	if (vma->vm_start == addr && vma->vm_ops == &shm_vm_ops) {
+	if (vma && vma->vm_start == addr && vma->vm_ops == &shm_vm_ops) {
 		do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start);
 		retval = 0;
 	}
-- 
1.7.11.7

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