5.4-stable review patch. If anyone has any objections, please let me know.
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From: David Sterba dsterba@suse.com
commit 9845664b9ee47ce7ee7ea93caf47d39a9d4552c4 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_44CA0665C9836EF9EEC80CB9E7E206DF... 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 --- fs/btrfs/dev-replace.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-)
--- a/fs/btrfs/dev-replace.c +++ b/fs/btrfs/dev-replace.c @@ -535,6 +535,23 @@ 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) { @@ -547,10 +564,9 @@ int btrfs_dev_replace_by_ioctl(struct bt 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,