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btrfs: dev-replace: properly validate device names

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commit 9845664b9e upstream.

There's a syzbot report that device name buffers passed to device
replace are not properly checked for string termination which could lead
to a read out of bounds in getname_kernel().

Add a helper that validates both source and target device name buffers.
For devid as the source initialize the buffer to empty string in case
something tries to read it later.

This was originally analyzed and fixed in a different way by Edward Adam
Davis (see links).

Link: https://lore.kernel.org/linux-btrfs/000000000000d1a1d1060cc9c5e7@google.com/
Link: https://lore.kernel.org/linux-btrfs/tencent_44CA0665C9836EF9EEC80CB9E7E206DF5206@qq.com/
CC: stable@vger.kernel.org # 4.19+
CC: Edward Adam Davis <eadavis@qq.com>
Reported-and-tested-by: syzbot+33f23b49ac24f986c9e8@syzkaller.appspotmail.com
Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
David Sterba 2024-02-14 16:19:24 +01:00 committed by Greg Kroah-Hartman
parent c34adc20b9
commit f590040ce2
1 changed files with 20 additions and 4 deletions
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24
fs/btrfs/dev-replace.c
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@ -740,6 +740,23 @@ leave:
return ret;
}
static int btrfs_check_replace_dev_names(struct btrfs_ioctl_dev_replace_args *args)
{
if (args->start.srcdevid == 0) {
if (memchr(args->start.srcdev_name, 0,
sizeof(args->start.srcdev_name)) == NULL)
return -ENAMETOOLONG;
} else {
args->start.srcdev_name[0] = 0;
}
if (memchr(args->start.tgtdev_name, 0,
sizeof(args->start.tgtdev_name)) == NULL)
return -ENAMETOOLONG;
return 0;
}
int btrfs_dev_replace_by_ioctl(struct btrfs_fs_info *fs_info,
struct btrfs_ioctl_dev_replace_args *args)
{
@ -752,10 +769,9 @@ int btrfs_dev_replace_by_ioctl(struct btrfs_fs_info *fs_info,
default:
return -EINVAL;
}
if ((args->start.srcdevid == 0 && args->start.srcdev_name[0] == '\0') ||
args->start.tgtdev_name[0] == '\0')
return -EINVAL;
ret = btrfs_check_replace_dev_names(args);
if (ret < 0)
return ret;
ret = btrfs_dev_replace_start(fs_info, args->start.tgtdev_name,
args->start.srcdevid,