mirrors/qemu
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

vvfat: Fix wrong checks for cluster mappings invariant

Browse Source 
How this `abort` was intended to check for was:
- if the `mapping->first_mapping_index` is not the same as
  `first_mapping_index`, which **should** happen only in one case,
  when we are handling the first mapping, in that case
  `mapping->first_mapping_index == -1`, in all other cases, the other
  mappings after the first should have the condition `true`.
- From above, we know that this is the first mapping, so if the offset
  is not `0`, then abort, since this is an invalid state.

The issue was that `first_mapping_index` is not set if we are
checking from the middle, the variable `first_mapping_index` is
only set if we passed through the check `cluster_was_modified` with the
first mapping, and in the same function call we checked the other
mappings.

One approach is to go into the loop even if `cluster_was_modified`
is not true so that we will be able to set `first_mapping_index` for the
first mapping, but since `first_mapping_index` is only used here,
another approach is to just check manually for the
`mapping->first_mapping_index != -1` since we know that this is the
value for the only entry where `offset == 0` (i.e. first mapping).

Signed-off-by: Amjad Alsharafi <amjadsharafi10@gmail.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <b0fbca3ee208c565885838f6a7deeaeb23f4f9c2.1721470238.git.amjadsharafi10@gmail.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Amjad Alsharafi 2024-07-20 18:13:32 +08:00 committed by Kevin Wolf
parent 21b25a0e46
commit f60a6f7e17
1 changed files with 2 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
block/vvfat.c
View File

@ -1880,7 +1880,6 @@ get_cluster_count_for_direntry(BDRVVVFATState* s, direntry_t* direntry, const ch
uint32_t cluster_num = begin_of_direntry(direntry);
uint32_t offset = 0;
int first_mapping_index = -1;
mapping_t* mapping = NULL;
const char* basename2 = NULL;
@ -1942,14 +1941,9 @@ get_cluster_count_for_direntry(BDRVVVFATState* s, direntry_t* direntry, const ch
if (strcmp(basename, basename2))
copy_it = 1;
first_mapping_index = array_index(&(s->mapping), mapping);
}
if (mapping->first_mapping_index != first_mapping_index
&& mapping->info.file.offset > 0) {
abort();
copy_it = 1;
}
assert(mapping->first_mapping_index == -1
|| mapping->info.file.offset > 0);
/* need to write out? */
if (!was_modified && is_file(direntry)) {