This is a note to let you know that I've just added the patch titled
ipc/shm: fix crash if CONFIG_SHMEM is not set
to the 4.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ipc-shm-fix-crash-if-config_shmem-is-not-set.patch
and it can be found in the queue-4.7 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 31b4beb473e3bdee1bf79db849502dcb24b5c202 Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Date: Mon, 19 Sep 2016 14:44:18 -0700
Subject: ipc/shm: fix crash if CONFIG_SHMEM is not set
From: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
commit 31b4beb473e3bdee1bf79db849502dcb24b5c202 upstream.
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@xxxxxxxxxxxxxxx
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reported-by: Tony Battersby <tonyb@xxxxxxxxxxxxxxx>
Tested-by: Tony Battersby <tonyb@xxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/ramfs/file-mmu.c | 9 +++++++++
1 file changed, 9 insertions(+)
--- 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_
.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 = {
Patches currently in stable-queue which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
queue-4.7/ipc-shm-fix-crash-if-config_shmem-is-not-set.patch
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