diff mbox series

[v5,1/5] vvfat: Fix bug in writing to middle of file

Message ID 4100134ef391cc33487ded6568bdf1a2abd1e8e7.1718195956.git.amjadsharafi10@gmail.com
State New
Headers show
Series vvfat: Fix write bugs for large files and add iotests | expand

Commit Message

Amjad Alsharafi June 12, 2024, 12:43 p.m. UTC 
Before this commit, the behavior when calling `commit_one_file` for
example with `offset=0x2000` (second cluster), what will happen is that
we won't fetch the next cluster from the fat, and instead use the first
cluster for the read operation.

This is due to off-by-one error here, where `i=0x2000 !< offset=0x2000`,
thus not fetching the next cluster.

Signed-off-by: Amjad Alsharafi <amjadsharafi10@gmail.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Tested-by: Kevin Wolf <kwolf@redhat.com>
---
 block/vvfat.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Michael Tokarev Aug. 11, 2024, 7:48 a.m. UTC | #1 
12.06.2024 15:43, Amjad Alsharafi wrote:
> Before this commit, the behavior when calling `commit_one_file` for
> example with `offset=0x2000` (second cluster), what will happen is that
> we won't fetch the next cluster from the fat, and instead use the first
> cluster for the read operation.
> 
> This is due to off-by-one error here, where `i=0x2000 !< offset=0x2000`,
> thus not fetching the next cluster.

This smells like a -stable material, despite the fact vvfat is generally
unreliable.  I'm picking this up for 7.2.x and 9.0.x.

Thanks,

/mjt
diff mbox series

Patch

diff --git a/block/vvfat.c b/block/vvfat.c
index 9d050ba3ae..19da009a5b 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -2525,8 +2525,9 @@  commit_one_file(BDRVVVFATState* s, int dir_index, uint32_t offset)
         return -1;
     }
 
-    for (i = s->cluster_size; i < offset; i += s->cluster_size)
+    for (i = 0; i < offset; i += s->cluster_size) {
         c = modified_fat_get(s, c);
+    }
 
     fd = qemu_open_old(mapping->path, O_RDWR | O_CREAT | O_BINARY, 0666);
     if (fd < 0) {