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vvfat: Fix reading files with non-continuous clusters

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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>
Message-ID: <1f3ea115779abab62ba32c788073cdc99f9ad5dd.1721470238.git.amjadsharafi10@gmail.com>
[kwolf: Simplified the patch based on Amjad's analysis and input]
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Amjad Alsharafi 2024-07-20 18:13:33 +08:00 committed by Kevin Wolf
parent f60a6f7e17
commit 5eed3db336
1 changed files with 2 additions and 1 deletions
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3
block/vvfat.c
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@ -1369,8 +1369,9 @@ static int open_file(BDRVVVFATState* s,mapping_t* mapping)
return -1; return -1;
vvfat_close_current_file(s); vvfat_close_current_file(s);
s->current_fd = fd; s->current_fd = fd;
s->current_mapping = mapping;
} }
s->current_mapping = mapping;
return 0; return 0;
} }