From: Mikulas Patocka mpatocka@redhat.com
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 --- drivers/md/dm-ioctl.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -655,7 +655,7 @@ static void list_version_get_needed(stru size_t *needed = needed_param;
*needed += sizeof(struct dm_target_versions); - *needed += strlen(tt->name); + *needed += strlen(tt->name) + 1; *needed += ALIGN_MASK; }
@@ -720,7 +720,7 @@ static int __list_versions(struct dm_ioc 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.