path: root/fs
diff options
authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2016-09-19 14:44:18 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-09-19 15:36:17 -0700
commit31b4beb473e3bdee1bf79db849502dcb24b5c202 (patch)
treeba862e325b07ebd106cde077dfbddd3aedf4b233 /fs
parentc8de641b1e9c5489aa6ca57b7836acd68e7563f1 (diff)
ipc/shm: fix crash if CONFIG_SHMEM is not set
Commit c01d5b300774 ("shmem: get_unmapped_area align huge page") makes use of shm_get_unmapped_area() in shm_file_operations() unconditional to CONFIG_MMU. As Tony Battersby pointed this can lead NULL-pointer dereference on machine with CONFIG_MMU=y and CONFIG_SHMEM=n. In this case ipc/shm is backed by ramfs which doesn't provide f_op->get_unmapped_area for configurations with MMU. The solution is to provide dummy f_op->get_unmapped_area for ramfs when CONFIG_MMU=y, which just call current->mm->get_unmapped_area(). Fixes: c01d5b300774 ("shmem: get_unmapped_area align huge page") Link: http://lkml.kernel.org/r/20160912102704.140442-1-kirill.shutemov@linux.intel.com Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reported-by: Tony Battersby <tonyb@cybernetics.com> Tested-by: Tony Battersby <tonyb@cybernetics.com> Cc: Hugh Dickins <hughd@google.com> Cc: <stable@vger.kernel.org> [4.7.x] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
1 files changed, 9 insertions, 0 deletions
diff --git a/fs/ramfs/file-mmu.c b/fs/ramfs/file-mmu.c
index 183a212694bf..12af0490322f 100644
--- a/fs/ramfs/file-mmu.c
+++ b/fs/ramfs/file-mmu.c
@@ -27,9 +27,17 @@
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/ramfs.h>
+#include <linux/sched.h>
#include "internal.h"
+static unsigned long ramfs_mmu_get_unmapped_area(struct file *file,
+ unsigned long addr, unsigned long len, unsigned long pgoff,
+ unsigned long flags)
+ return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
const struct file_operations ramfs_file_operations = {
.read_iter = generic_file_read_iter,
.write_iter = generic_file_write_iter,
@@ -38,6 +46,7 @@ const struct file_operations ramfs_file_operations = {
.splice_read = generic_file_splice_read,
.splice_write = iter_file_splice_write,
.llseek = generic_file_llseek,
+ .get_unmapped_area = ramfs_mmu_get_unmapped_area,
const struct inode_operations ramfs_file_inode_operations = {