From c177d3dc50d59042b1756e352e19f2dd8b01c25a Mon Sep 17 00:00:00 2001 From: Taylor Blau Date: Thu, 26 Sep 2024 11:22:41 -0400 Subject: pack-objects: use finalize_object_file() to rename pack/idx/etc In most places that write files to the object database (even packfiles via index-pack or fast-import), we use finalize_object_file(). This prefers link()/unlink() over rename(), because it means we will prefer data that is already in the repository to data that we are newly writing. We should do the same thing in pack-objects. Even though we don't think of it as accepting outside data (and thus not being susceptible to collision attacks), in theory a determined attacker could present just the right set of objects to cause an incremental repack to generate a pack with their desired hash. This has some test and real-world fallout, as seen in the adjustment to t5303 below. That test script assumes that we can "fix" corruption by repacking into a good state, including when the pack generated by that repack operation collides with a (corrupted) pack with the same hash. This violates our assumption from the previous adjustments to finalize_object_file() that if we're moving a new file over an existing one, that since their checksums match, so too must their contents. This makes "fixing" corruption like this a more explicit operation, since the test (and users, who may fix real-life corruption using a similar technique) must first move the broken contents out of the way. Note also that we now call adjust_shared_perm() twice. We already call adjust_shared_perm() in stage_tmp_packfiles(), and now call it again in finalize_object_file(). This is somewhat wasteful, but cleaning up the existing calls to adjust_shared_perm() is tricky (because sometimes we're writing to a tmpfile, and sometimes we're writing directly into the final destination), so let's tolerate some minor waste until we can more carefully clean up the now-redundant calls. Co-authored-by: Jeff King Signed-off-by: Jeff King Signed-off-by: Taylor Blau Signed-off-by: Junio C Hamano --- pack-write.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'pack-write.c') diff --git a/pack-write.c b/pack-write.c index d07f03d0ab..e5beecd3a4 100644 --- a/pack-write.c +++ b/pack-write.c @@ -8,6 +8,7 @@ #include "csum-file.h" #include "remote.h" #include "chunk-format.h" +#include "object-file.h" #include "pack-mtimes.h" #include "pack-objects.h" #include "pack-revindex.h" @@ -527,9 +528,9 @@ static void rename_tmp_packfile(struct strbuf *name_prefix, const char *source, size_t name_prefix_len = name_prefix->len; strbuf_addstr(name_prefix, ext); - if (rename(source, name_prefix->buf)) - die_errno("unable to rename temporary file to '%s'", - name_prefix->buf); + if (finalize_object_file(source, name_prefix->buf)) + die("unable to rename temporary file to '%s'", + name_prefix->buf); strbuf_setlen(name_prefix, name_prefix_len); } -- cgit v1.3