From: Mikulas Patocka <mpatocka@redhat.com> stable inclusion from stable-v4.19.267 commit 3a1c35d72dc0b34d1e746ed705790c0f630aa427 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IC5BWC CVE: CVE-2022-49771 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... ------------------ commit 4fe1ec995483737f3d2a14c3fe1d8fe634972979 upstream. __list_versions will first estimate the required space using the "dm_target_iterate(list_version_get_needed, &needed)" call and then will fill the space using the "dm_target_iterate(list_version_get_info, &iter_info)" call. Each of these calls locks the targets using the "down_read(&_lock)" and "up_read(&_lock)" calls, however between the first and second "dm_target_iterate" there is no lock held and the target modules can be loaded at this point, so the second "dm_target_iterate" call may need more space than what was the first "dm_target_iterate" returned. The code tries to handle this overflow (see the beginning of list_version_get_info), however this handling is incorrect. The code sets "param->data_size = param->data_start + needed" and "iter_info.end = (char *)vers+len" - "needed" is the size returned by the first dm_target_iterate call; "len" is the size of the buffer allocated by userspace. "len" may be greater than "needed"; in this case, the code will write up to "len" bytes into the buffer, however param->data_size is set to "needed", so it may write data past the param->data_size value. The ioctl interface copies only up to param->data_size into userspace, thus part of the result will be truncated. Fix this bug by setting "iter_info.end = (char *)vers + needed;" - this guarantees that the second "dm_target_iterate" call will write only up to the "needed" buffer and it will exit with "DM_BUFFER_FULL_FLAG" if it overflows the "needed" space - in this case, userspace will allocate a larger buffer and retry. Note that there is also a bug in list_version_get_needed - we need to add "strlen(tt->name) + 1" to the needed size, not "strlen(tt->name)". Cc: stable@vger.kernel.org Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Zheng Qixing <zhengqixing@huawei.com> --- drivers/md/dm-ioctl.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index c8c27d23bb45..2b00359e4825 100644 --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -573,7 +573,7 @@ static void list_version_get_needed(struct target_type *tt, void *needed_param) size_t *needed = needed_param; *needed += sizeof(struct dm_target_versions); - *needed += strlen(tt->name); + *needed += strlen(tt->name) + 1; *needed += ALIGN_MASK; } @@ -628,7 +628,7 @@ static int list_versions(struct file *filp, struct dm_ioctl *param, size_t param iter_info.old_vers = NULL; iter_info.vers = vers; iter_info.flags = 0; - iter_info.end = (char *)vers+len; + iter_info.end = (char *)vers + needed; /* * Now loop through filling out the names & versions. -- 2.39.2