[PULL,11/13] vvfat: Fix reading files with non-continuous clusters

Commit Message

Kevin Wolf Aug. 5, 2024, 9:08 p.m. UTC

From: Amjad Alsharafi <[e-mail]>

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 <[e-mail]>
Message-ID: <1f3ea1[e-mail]>
[kwolf: Simplified the patch based on Amjad's analysis and input]
Signed-off-by: Kevin Wolf <[e-mail]>
---
 block/vvfat.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Patch

diff --git a/block/vvfat.c b/block/vvfat.c
index e3a83fbc88..8ffe8b3b9b 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -1369,8 +1369,9 @@  static int open_file(BDRVVVFATState* s,mapping_t* mapping)
             return -1;
         vvfat_close_current_file(s);
         s->current_fd = fd;
-        s->current_mapping = mapping;
     }
+
+    s->current_mapping = mapping;
     return 0;
 }