[CHKDSK][VFATLIB] Chkdsk, fix writes to wrong disk offsets

Doug-Lyons · Doug-Lyons · commit 3f4a7e356ee2 · 2026-04-03T19:57:01.000-05:00
diff --git a/sdk/lib/fslib/vfatlib/check/io.c b/sdk/lib/fslib/vfatlib/check/io.c
@@ -374,6 +374,9 @@ void fs_write(off_t pos, int size, void *data)
             memcpy((char *)scratch + seek_delta, data, size);
         }
 
+        /* Seek back to the beginning of our read/write */ 
+        if (lseek(fd, seekpos_aligned, 0) != seekpos_aligned) pdie("Seek to %lld",seekpos_aligned);
+
         /* Write it back */
         if ((did = write(fd, scratch, readsize_aligned)) == (int)readsize_aligned)
         {

Original file line number	Diff line number	Diff line change
`@@ -374,6 +374,9 @@ void fs_write(off_t pos, int size, void *data)`
`374`	`374`	`memcpy((char *)scratch + seek_delta, data, size);`
`375`	`375`	`}`
`376`	`376`
	`377`	`+ /* Seek back to the beginning of our read/write */`
	`378`	`+ if (lseek(fd, seekpos_aligned, 0) != seekpos_aligned) pdie("Seek to %lld",seekpos_aligned);`
	`379`	`+`
`377`	`380`	`/* Write it back */`
`378`	`381`	`if ((did = write(fd, scratch, readsize_aligned)) == (int)readsize_aligned)`
`379`	`382`	`{`