I noticed the issue in the commit message 'ffvat' should be 'vvfat',
I'll fix it in the next version.
On Thu, Mar 28, 2024 at 04:11:27AM +0800, Amjad Alsharafi wrote:
> When reading with `read_cluster` we get the `mapping` with
> `find_mapping_for_cluster` and then we call `open_file` for this
> mapping.
> The issue appear when its the same file, but a second cluster that is
> not immediately after it, imagine clusters `500 -> 503`, this will give
> us 2 mappings one has the range `500..501` and another `503..504`, both
> point to the same file, but different offsets.
>
> When we don't open the file since the path is the same, we won't assign
> `s->current_mapping` and thus accessing way out of bound of the file.
>
> From our example above, after `open_file` (that didn't open anything) we
> will get the offset into the file with
> `s->cluster_size*(cluster_num-s->current_mapping->begin)`, which will
> give us `0x2000 * (504-500)`, which is out of bound for this mapping and
> will produce some issues.
>
> Signed-off-by: Amjad Alsharafi <amjadsharaf...@gmail.com>
> ---
> block/vvfat.c | 21 ++++++++++++++-------
> 1 file changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/block/vvfat.c b/block/vvfat.c
> index cb3ab81e29..87165abc26 100644
> --- a/block/vvfat.c
> +++ b/block/vvfat.c
> @@ -1360,15 +1360,22 @@ static int open_file(BDRVVVFATState* s,mapping_t*
> mapping)
> {
> if(!mapping)
> return -1;
> + int new_path = 1;
> if(!s->current_mapping ||
> - strcmp(s->current_mapping->path,mapping->path)) {
> - /* open file */
> - int fd = qemu_open_old(mapping->path,
> +
> s->current_mapping->first_mapping_index!=mapping->first_mapping_index ||
> + (new_path = strcmp(s->current_mapping->path,mapping->path))) {
> +
> + if (new_path) {
> + /* open file */
> + int fd = qemu_open_old(mapping->path,
> O_RDONLY | O_BINARY | O_LARGEFILE);
> - if(fd<0)
> - return -1;
> - vvfat_close_current_file(s);
> - s->current_fd = fd;
> + if(fd<0)
> + return -1;
> + vvfat_close_current_file(s);
> +
> + s->current_fd = fd;
> + }
> + assert(s->current_fd);
> s->current_mapping = mapping;
> }
> return 0;
> --
> 2.44.0
>
