| Message ID | 20240327201231.31046-4-amjadsharafi10@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | vvfat: Fix bugs in writing and reading files | expand |
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 <amjadsharafi10@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 >
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;
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 <amjadsharafi10@gmail.com> --- block/vvfat.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-)