From fd7c092e711ebab55b2688d3859d95dfd0301f73 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Fri, 1 Mar 2013 22:45:44 +0000 Subject: dm: fix truncated status strings Avoid returning a truncated table or status string instead of setting the DM_BUFFER_FULL_FLAG when the last target of a table fills the buffer. When processing a table or status request, the function retrieve_status calls ti->type->status. If ti->type->status returns non-zero, retrieve_status assumes that the buffer overflowed and sets DM_BUFFER_FULL_FLAG. However, targets don't return non-zero values from their status method on overflow. Most targets returns always zero. If a buffer overflow happens in a target that is not the last in the table, it gets noticed during the next iteration of the loop in retrieve_status; but if a buffer overflow happens in the last target, it goes unnoticed and erroneously truncated data is returned. In the current code, the targets behave in the following way: * dm-crypt returns -ENOMEM if there is not enough space to store the key, but it returns 0 on all other overflows. * dm-thin returns errors from the status method if a disk error happened. This is incorrect because retrieve_status doesn't check the error code, it assumes that all non-zero values mean buffer overflow. * all the other targets always return 0. This patch changes the ti->type->status function to return void (because most targets don't use the return code). Overflow is detected in retrieve_status: if the status method fills up the remaining space completely, it is assumed that buffer overflow happened. Cc: stable@vger.kernel.org Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon --- drivers/md/dm-ioctl.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) (limited to 'drivers/md/dm-ioctl.c') diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c index 0666b5d14b88..eee353da3742 100644 --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -1067,6 +1067,7 @@ static void retrieve_status(struct dm_table *table, num_targets = dm_table_get_num_targets(table); for (i = 0; i < num_targets; i++) { struct dm_target *ti = dm_table_get_target(table, i); + size_t l; remaining = len - (outptr - outbuf); if (remaining <= sizeof(struct dm_target_spec)) { @@ -1093,14 +1094,17 @@ static void retrieve_status(struct dm_table *table, if (ti->type->status) { if (param->flags & DM_NOFLUSH_FLAG) status_flags |= DM_STATUS_NOFLUSH_FLAG; - if (ti->type->status(ti, type, status_flags, outptr, remaining)) { - param->flags |= DM_BUFFER_FULL_FLAG; - break; - } + ti->type->status(ti, type, status_flags, outptr, remaining); } else outptr[0] = '\0'; - outptr += strlen(outptr) + 1; + l = strlen(outptr) + 1; + if (l == remaining) { + param->flags |= DM_BUFFER_FULL_FLAG; + break; + } + + outptr += l; used = param->data_start + (outptr - outbuf); outptr = align_ptr(outptr); -- cgit v1.2.3