|
From: | Max Reitz |
Subject: | Re: [Qemu-devel] [PATCH v6 06/11] qcow2: Fix refcount blocks beyond image end |
Date: | Tue, 21 Oct 2014 09:14:02 +0200 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 |
On 2014-10-20 at 18:44, Kevin Wolf wrote:
Am 20.10.2014 um 16:35 hat Max Reitz geschrieben:If the qcow2 check function detects a refcount block located beyond the image end, grow the image appropriately. This cannot break anything and is the logical fix for such a case. Signed-off-by: Max Reitz <address@hidden> Reviewed-by: Eric Blake <address@hidden> --- block/qcow2-refcount.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 58 insertions(+), 4 deletions(-) diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index 55a539f..0225769 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -1544,7 +1544,8 @@ static int check_refblocks(BlockDriverState *bs, BdrvCheckResult *res, int64_t *nb_clusters) { BDRVQcowState *s = bs->opaque; - int64_t i; + int64_t i, size; + int ret;for(i = 0; i < s->refcount_table_size; i++) {uint64_t offset, cluster; @@ -1560,9 +1561,62 @@ static int check_refblocks(BlockDriverState *bs, BdrvCheckResult *res, }if (cluster >= *nb_clusters) {- fprintf(stderr, "ERROR refcount block %" PRId64 - " is outside image\n", i); - res->corruptions++; + fprintf(stderr, "%s refcount block %" PRId64 " is outside image\n", + fix & BDRV_FIX_ERRORS ? "Repairing" : "ERROR", i); + + if (fix & BDRV_FIX_ERRORS) { + int64_t old_nb_clusters = *nb_clusters; + + if (offset + s->cluster_size < offset || + offset + s->cluster_size > INT64_MAX)I _think_ this code is correct because offset is unsigned, but it would be easier and not rely on overflow semantics like this: if (offset > INT64_MAX - s->cluster_size)
Okay.
+ { + ret = -EINVAL; + goto resize_fail; + } + + ret = bdrv_truncate(bs->file, offset + s->cluster_size); + if (ret < 0) { + goto resize_fail; + } + size = bdrv_getlength(bs->file); + if (size < 0) { + ret = size; + goto resize_fail; + } + + *nb_clusters = size_to_clusters(s, size); + assert(*nb_clusters >= old_nb_clusters); + + *refcount_table = g_try_realloc(*refcount_table, + *nb_clusters * sizeof(uint16_t)); + if (!*refcount_table) { + res->check_errors++; + return -ENOMEM; + } + + memset(*refcount_table + old_nb_clusters, 0, + (*nb_clusters - old_nb_clusters) * sizeof(uint16_t));Considering the comments you got in previous comments, sizeof(**refcount_table) might make it more obvious what's going on, and would also be more robust against later changes of the type.
I highly doubt I'll change the type so that sizeof(**refcount_table) works. If variable refcounts are implemented, I'll probably make *refcount_table just a void * and then access its elements through a function; sadly, qemu's make doesn't error out against sizeof(void) (which would be -Wpointer-arith or just -pedantic), so just using sizeof(**refcount_table) so that everything throws an error once it's a void ** won't work.
I guess I'll change it in a v7 because sizeof(**refcount_table) is easier to grep for than sizeof(uint16_t).
+ if (cluster >= *nb_clusters) { + ret = -EINVAL; + goto resize_fail; + } + + res->corruptions_fixed++; + inc_refcounts(bs, res, *refcount_table, *nb_clusters, + offset, s->cluster_size); + /* No need to check whether the refcount is now greater than 1: + * This area was just allocated and zeroed, so it can only be + * exactly 1 after inc_refcounts() */ + continue; + +resize_fail: + res->corruptions++; + fprintf(stderr, "ERROR could not resize image: %s\n", + strerror(-ret)); + } else { + res->corruptions++; + } continue; }Reviewed-by: Kevin Wolf <address@hidden>
Thanks! Max
[Prev in Thread] | Current Thread | [Next in Thread] |