(tar_short_read): fix undefined behaviour.

aborodin · aborodin · commit e0d803e95a05 · 2025-06-19T21:04:31.000+03:00
Use (char *) record_start, instead of record_start-&gt;buffer, to avoid
undefined behavior accessing past end of buffer. In practice the
undefined behavior is harmless unless running with -fsanitize=undefined
or a similarly-picky implementation.

Sync with GNU tar 7d96e820a52531097db23f38725e178a9f7d66b0.

Signed-off-by: Andrew Borodin &lt;aborodin@vmail.ru&gt;
diff --git a/src/vfs/tar/tar-internal.c b/src/vfs/tar/tar-internal.c
@@ -85,8 +85,8 @@ tar_short_read (size_t status, tar_super_t *archive)
     size_t left;  // bytes left
     char *more;   // pointer to next byte to read
 
-    more = archive->record_start->buffer + status;
     left = record_size - status;
+    more = (char *) archive->record_start + status;
 
     while (left % BLOCKSIZE != 0 || (left != 0 && status != 0))
     {

Original file line number	Diff line number	Diff line change
`@@ -85,8 +85,8 @@ tar_short_read (size_t status, tar_super_t *archive)`
`85`	`85`	`size_t left; // bytes left`
`86`	`86`	`char *more; // pointer to next byte to read`
`87`	`87`
`88`		`- more = archive->record_start->buffer + status;`
`89`	`88`	`left = record_size - status;`
	`89`	`+ more = (char *) archive->record_start + status;`
`90`	`90`
`91`	`91`	`while (left % BLOCKSIZE != 0 \|\| (left != 0 && status != 0))`
`92`	`92`	`{`