autofs: fix autofs_sbi() does not check super block type

autofs_sbi() does not check the superblock magic number to verify it has been given an autofs super block. Link: http://lkml.kernel.org/r/153475422934.17131.7563724552005298277.stgit@pluto.themaw.net Reported-by: <syzbot+87c3c541582e56943277@syzkaller.appspotmail.com> Signed-off-by: Ian Kent <raven@themaw.net> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
DX37 · Aug 22, 2018 · 0633da4 · 0633da4
1 parent 778a339
commit 0633da4
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Showing 2 changed files with 3 additions and 2 deletions.
diff --git a/fs/autofs/autofs_i.h b/fs/autofs/autofs_i.h
@@ -26,6 +26,7 @@
 #include <linux/list.h>
 #include <linux/completion.h>
 #include <linux/file.h>
+#include <linux/magic.h>
 
 /* This is the range of ioctl() numbers we claim as ours */
 #define AUTOFS_IOC_FIRST     AUTOFS_IOC_READY
@@ -124,7 +125,8 @@ struct autofs_sb_info {
 
 static inline struct autofs_sb_info *autofs_sbi(struct super_block *sb)
 {
-	return (struct autofs_sb_info *)(sb->s_fs_info);
+	return sb->s_magic != AUTOFS_SUPER_MAGIC ?
+		NULL : (struct autofs_sb_info *)(sb->s_fs_info);
 }
 
 static inline struct autofs_info *autofs_dentry_ino(struct dentry *dentry)

diff --git a/fs/autofs/inode.c b/fs/autofs/inode.c
@@ -10,7 +10,6 @@
 #include <linux/seq_file.h>
 #include <linux/pagemap.h>
 #include <linux/parser.h>
-#include <linux/magic.h>
 
 #include "autofs_i.h"