From: Maxim Suhanov Date: Mon, 28 Aug 2023 16:38:19 +0300 Subject: fs/ntfs: Fix an OOB read when parsing a volume label This fix introduces checks to ensure that an NTFS volume label is always read from the corresponding file record segment. The current NTFS code allows the volume label string to be read from an arbitrary, attacker-chosen memory location. However, the bytes read are always treated as UTF-16LE. So, the final string displayed is mostly unreadable and it can't be easily converted back to raw bytes. The lack of this check is a minor issue, likely not causing a significant data leak. Reported-by: Maxim Suhanov Signed-off-by: Maxim Suhanov Reviewed-by: Daniel Kiper --- grub-core/fs/ntfs.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/grub-core/fs/ntfs.c b/grub-core/fs/ntfs.c index bb70c89..ff5e374 100644 --- a/grub-core/fs/ntfs.c +++ b/grub-core/fs/ntfs.c @@ -1213,13 +1213,29 @@ grub_ntfs_label (grub_device_t device, char **label) init_attr (&mft->attr, mft); pa = find_attr (&mft->attr, GRUB_NTFS_AT_VOLUME_NAME); + + if (pa >= mft->buf + (mft->data->mft_size << GRUB_NTFS_BLK_SHR)) + { + grub_error (GRUB_ERR_BAD_FS, "can\'t parse volume label"); + goto fail; + } + + if (mft->buf + (mft->data->mft_size << GRUB_NTFS_BLK_SHR) - pa < 0x16) + { + grub_error (GRUB_ERR_BAD_FS, "can\'t parse volume label"); + goto fail; + } + if ((pa) && (pa[8] == 0) && (u32at (pa, 0x10))) { int len; len = u32at (pa, 0x10) / 2; pa += u16at (pa, 0x14); - *label = get_utf8 (pa, len); + if (mft->buf + (mft->data->mft_size << GRUB_NTFS_BLK_SHR) - pa >= 2 * len) + *label = get_utf8 (pa, len); + else + grub_error (GRUB_ERR_BAD_FS, "can\'t parse volume label"); } fail: