From: David Sterba dsterba@suse.com

stable inclusion from stable-v5.10.167 commit 2886fe308a83968dde252302884a1e63351cf16d category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9E469 CVE: CVE-2024-26791

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=l...

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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 Signed-off-by: Long Li leo.lilong@huawei.com --- fs/btrfs/dev-replace.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c index be6935d19197..9a6055659c1a 100644 --- a/fs/btrfs/dev-replace.c +++ b/fs/btrfs/dev-replace.c @@ -566,6 +566,23 @@ static int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info, 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) { @@ -578,10 +595,9 @@ 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,