mirrors/git
1
0
Fork 0
mirror of https://github.com/git/git.git synced 2024-10-28 04:49:43 +01:00
Code Activity

finalize_object_file(): check for name collision before renaming

Browse source 
We prefer link()/unlink() to rename() for object files, with the idea
that we should prefer the data that is already on disk to what is
incoming. But we may fall back to rename() if the user has configured us
to do so, or if the filesystem seems not to support cross-directory
links. This loses the "prefer what is on disk" property.

We can mitigate this somewhat by trying to stat() the destination
filename before doing the rename. This is racy, since the object could
be created between the stat() and rename() calls. But in practice it is
expanding the definition of "what is already on disk" to be the point
that the function is called. That is enough to deal with any potential
attacks where an attacker is trying to collide hashes with what's
already in the repository.

Co-authored-by: Jeff King <peff@peff.net>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Taylor Blau 2024-09-26 11:22:32 -04:00 committed by Junio C Hamano
parent 2e7b89e038
commit d1b44bb764
1 changed files with 6 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

8
object-file.c
View file

@ -1904,6 +1904,7 @@ static void write_object_file_prepare_literally(const struct git_hash_algo *algo
*/
int finalize_object_file(const char *tmpfile, const char *filename)
{
struct stat st;
int ret = 0;
if (object_creation_mode == OBJECT_CREATION_USES_RENAMES)
@ -1924,9 +1925,12 @@ int finalize_object_file(const char *tmpfile, const char *filename)
*/
if (ret && ret != EEXIST) {
try_rename:
if (!rename(tmpfile, filename))
if (!stat(filename, &st))
ret = EEXIST;
else if (!rename(tmpfile, filename))
goto out;
ret = errno;
else
ret = errno;
}
unlink_or_warn(tmpfile);
if (ret) {