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fat: fix uninit-memory access for partial initialized inode 

When get an error in the middle of reading an inode, some fields in the
inode might be still not initialized.  And then the evict_inode path may
access those fields via iput().

To fix, this makes sure that inode fields are initialized.

Reported-by: syzbot+9d82b8de2992579da5d0@syzkaller.appspotmail.com
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/871rqnreqx.fsf@mail.parknet.co.jp
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
OGAWA Hirofumi 2020-03-05 22:28:36 -08:00 committed by Linus Torvalds
parent c3e5ea6ee5
commit bc87302a09
1 changed files with 7 additions and 12 deletions
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19
fs/fat/inode.c
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@ -750,6 +750,13 @@ static struct inode *fat_alloc_inode(struct super_block *sb)
return NULL;
init_rwsem(&ei->truncate_lock);
/* Zeroing to allow iput() even if partial initialized inode. */
ei->mmu_private = 0;
ei->i_start = 0;
ei->i_logstart = 0;
ei->i_attrs = 0;
ei->i_pos = 0;
return &ei->vfs_inode;
}
@ -1374,16 +1381,6 @@ out:
return 0;
}
static void fat_dummy_inode_init(struct inode *inode)
{
/* Initialize this dummy inode to work as no-op. */
MSDOS_I(inode)->mmu_private = 0;
MSDOS_I(inode)->i_start = 0;
MSDOS_I(inode)->i_logstart = 0;
MSDOS_I(inode)->i_attrs = 0;
MSDOS_I(inode)->i_pos = 0;
}
static int fat_read_root(struct inode *inode)
{
struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
@ -1844,13 +1841,11 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat,
fat_inode = new_inode(sb);
if (!fat_inode)
goto out_fail;
fat_dummy_inode_init(fat_inode);
sbi->fat_inode = fat_inode;
fsinfo_inode = new_inode(sb);
if (!fsinfo_inode)
goto out_fail;
fat_dummy_inode_init(fsinfo_inode);
fsinfo_inode->i_ino = MSDOS_FSINFO_INO;
sbi->fsinfo_inode = fsinfo_inode;
insert_inode_hash(fsinfo_inode);