[PATCH 4.18 220/350] ext4: fix EXT4_IOC_SWAP_BOOT

Greg Kroah-Hartman
2018-11-11T23:25:02Z

From: Theodore Ts'o <tytso@mit.edu>

commit 18aded17492088962ef43f00825179598b3e8c58 upstream.

The code EXT4_IOC_SWAP_BOOT ioctl hasn't been updated in a while, and
it's a bit broken with respect to more modern ext4 kernels, especially
metadata checksums.

Other problems fixed with this commit:

* Don't allow installing a DAX, swap file, or an encrypted file as a
boot loader.

* Respect the immutable and append-only flags.

* Wait until any DIO operations are finished *before* calling
truncate_inode_pages().

* Don't swap inode->i_flags, since these flags have nothing to do with
the inode blocks --- and it will give the IMA/audit code heartburn
when the inode is evicted.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Reported-by: syzbot+e81ccd4744c6c4f71354@syzkaller.appspotmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/ext4/ioctl.c | 33 +++++++++++++++++++++++++++------
1 file changed, 27 insertions(+), 6 deletions(-)

--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -67,7 +67,6 @@ static void swap_inode_data(struct inode
ei1 = EXT4_I(inode1);
ei2 = EXT4_I(inode2);

- swap(inode1->i_flags, inode2->i_flags);
swap(inode1->i_version, inode2->i_version);
swap(inode1->i_blocks, inode2->i_blocks);
swap(inode1->i_bytes, inode2->i_bytes);
@@ -85,6 +84,21 @@ static void swap_inode_data(struct inode
i_size_write(inode2, isize);
}

+static void reset_inode_seed(struct inode *inode)
+{
+ struct ext4_inode_info *ei = EXT4_I(inode);
+ struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+ __le32 inum = cpu_to_le32(inode->i_ino);
+ __le32 gen = cpu_to_le32(inode->i_generation);
+ __u32 csum;
+
+ if (!ext4_has_metadata_csum(inode->i_sb))
+ return;
+
+ csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&inum, sizeof(inum));
+ ei->i_csum_seed = ext4_chksum(sbi, csum, (__u8 *)&gen, sizeof(gen));
+}
+
/**
* Swap the information from the given @inode and the inode
* EXT4_BOOT_LOADER_INO. It will basically swap i_data and all other
@@ -102,10 +116,13 @@ static long swap_inode_boot_loader(struc
struct inode *inode_bl;
struct ext4_inode_info *ei_bl;

- if (inode->i_nlink != 1 || !S_ISREG(inode->i_mode))
+ if (inode->i_nlink != 1 || !S_ISREG(inode->i_mode) ||
+ IS_SWAPFILE(inode) || IS_ENCRYPTED(inode) ||
+ ext4_has_inline_data(inode))
return -EINVAL;

- if (!inode_owner_or_capable(inode) || !capable(CAP_SYS_ADMIN))
+ if (IS_RDONLY(inode) || IS_APPEND(inode) || IS_IMMUTABLE(inode) ||
+ !inode_owner_or_capable(inode) || !capable(CAP_SYS_ADMIN))
return -EPERM;

inode_bl = ext4_iget(sb, EXT4_BOOT_LOADER_INO);
@@ -120,13 +137,13 @@ static long swap_inode_boot_loader(struc
* that only 1 swap_inode_boot_loader is running. */
lock_two_nondirectories(inode, inode_bl);

- truncate_inode_pages(&inode->i_data, 0);
- truncate_inode_pages(&inode_bl->i_data, 0);
-
/* Wait for all existing dio workers */
inode_dio_wait(inode);
inode_dio_wait(inode_bl);

+ truncate_inode_pages(&inode->i_data, 0);
+ truncate_inode_pages(&inode_bl->i_data, 0);
+
handle = ext4_journal_start(inode_bl, EXT4_HT_MOVE_EXTENTS, 2);
if (IS_ERR(handle)) {
err = -EINVAL;
@@ -159,6 +176,8 @@ static long swap_inode_boot_loader(struc

inode->i_generation = prandom_u32();
inode_bl->i_generation = prandom_u32();
+ reset_inode_seed(inode);
+ reset_inode_seed(inode_bl);

ext4_discard_preallocations(inode);

@@ -169,6 +188,7 @@ static long swap_inode_boot_loader(struc
inode->i_ino, err);
/* Revert all changes: */
swap_inode_data(inode, inode_bl);
+ ext4_mark_inode_dirty(handle, inode);
} else {
err = ext4_mark_inode_dirty(handle, inode_bl);
if (err < 0) {
@@ -178,6 +198,7 @@ static long swap_inode_boot_loader(struc
/* Revert all changes: */
swap_inode_data(inode, inode_bl);
ext4_mark_inode_dirty(handle, inode);
+ ext4_mark_inode_dirty(handle, inode_bl);
}
}
ext4_journal_stop(handle);