From: Dave Hansen <[email protected]>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 07a46ed27dc6344de831a450df82336270a157a9 upstream.

Andrew Morton noted

        
http://lkml.kernel.org/r/[email protected]

that the shmdt uses inode->i_size outside of i_mutex being held.
There is one more case in shm.c in shm_destroy().  This converts
both users over to use i_size_read().

Signed-off-by: Dave Hansen <[email protected]>
Cc: Manfred Spraul <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Jiri Slaby <[email protected]>
---
 ipc/shm.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/ipc/shm.c b/ipc/shm.c
index b039a85e2b8d..623bc3877118 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -218,7 +218,8 @@ static void shm_destroy(struct ipc_namespace *ns, struct 
shmid_kernel *shp)
        if (!is_file_hugepages(shm_file))
                shmem_lock(shm_file, 0, shp->mlock_user);
        else if (shp->mlock_user)
-               user_shm_unlock(file_inode(shm_file)->i_size, shp->mlock_user);
+               user_shm_unlock(i_size_read(file_inode(shm_file)),
+                               shp->mlock_user);
        fput(shm_file);
        ipc_rcu_putref(shp, shm_rcu_free);
 }
@@ -1278,7 +1279,7 @@ SYSCALL_DEFINE1(shmdt, char __user *, shmaddr)
                         * in the range we are unmapping.
                         */
                        file = vma->vm_file;
-                       size = file_inode(file)->i_size;
+                       size = i_size_read(file_inode(vma->vm_file));
                        do_munmap(mm, vma->vm_start, vma->vm_end - 
vma->vm_start);
                        /*
                         * We discovered the size of the shm segment, so
-- 
2.3.4

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