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fat: fix uninit-memory access for partial initialized inode

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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);