linux-kernel - [PATCH 3.12 078/155] shmdt: use i_size_read() instead of ->i

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Date:	Tue,  7 Apr 2015 14:50:47 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Manfred Spraul <manfred@...orfullife.com>,
	Davidlohr Bueso <dave@...olabs.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 078/155] shmdt: use i_size_read() instead of ->i_size

From: Dave Hansen <dave.hansen@...ux.intel.com>

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/20141104142027.a7a0d010772d84560b445f59@linux-foundation.org

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 <dave.hansen@...ux.intel.com>
Cc: Manfred Spraul <manfred@...orfullife.com>
Cc: Davidlohr Bueso <dave@...olabs.net>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 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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