Subject: [PATCH 3/3] repack: check error writing to pack-objects subprocess

From: Junio C Hamano <[email-masked]>
Date: Sat, 2 Mar 2024 11:03:48 -0800

When "git repack" repacks promisor objects, it starts a pack-objects
subprocess and uses xwrite() to send object names over the pipe to
it, but without any error checking.  An I/O error or short write
(even though a short write is unlikely for such a small amount of
data) can result in a packfile that lacks certain objects we wanted
to put in there, leading to a silent repository corruption.

Use write_in_full(), instead of xwrite(), to mitigate short write
risks, check errors from it, and abort if we see a failure.

Signed-off-by: Junio C Hamano <[email-masked]>
---
 builtin/repack.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/builtin/repack.c b/builtin/repack.c
index ede36328a3..15e4cccc45 100644
--- a/builtin/repack.c
+++ b/builtin/repack.c
@@ -314,8 +314,9 @@ static int write_oid(const struct object_id *oid,
 			die(_("could not start pack-objects to repack promisor objects"));
 	}
 
-	xwrite(cmd->in, oid_to_hex(oid), the_hash_algo->hexsz);
-	xwrite(cmd->in, "\n", 1);
+	if (write_in_full(cmd->in, oid_to_hex(oid), the_hash_algo->hexsz) < 0 ||
+	    write_in_full(cmd->in, "\n", 1) < 0)
+		die(_("failed to feed promisor objects to pack-objects"));
 	return 0;
 }
 
-- 
2.44.0-84-gb387623c12