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From: Jeff King <>
Cc: Jonathan Tan <>,
	Masaya Suzuki <>
Subject: [PATCH 4/7] pkt-line: prepare buffer before handling ERR packets
Date: Sat, 13 Apr 2019 01:54:02 -0400	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Since 2d103c31c2 (pack-protocol.txt: accept error packets in any
context, 2018-12-29), the pktline code will detect an ERR packet and die
automatically, saving the caller from dealing with it. But we do so too
early in the function, before we have terminated the buffer with a NUL.

As a result, passing the ERR message to die() may result in us printing
random cruft from a previous packet. This doesn't trigger memory tools
like ASan because we reuse the same buffer over and over (so the
contents are valid and initialized; they're just stale).

We can see demonstrate this by tightening the regex we use to match the
error message in t5516; without this patch, git-fetch will accidentally
print the capabilities from the (much longer) initial packet we

By moving the ERR code later in the function we get a few other
benefits, too:

  - we'll now chomp any newline sent by the other side (which is what we
    want, since die() will add its own newline)

  - we'll now mention the ERR packet with GIT_TRACE_PACKET

Signed-off-by: Jeff King <>
 pkt-line.c            | 9 +++++----
 t/ | 2 +-
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/pkt-line.c b/pkt-line.c
index ffd7220544..c9ed780d0b 100644
--- a/pkt-line.c
+++ b/pkt-line.c
@@ -350,16 +350,17 @@ enum packet_read_status packet_read_with_status(int fd, char **src_buffer,
 		return PACKET_READ_EOF;
-	if ((options & PACKET_READ_DIE_ON_ERR_PACKET) &&
-	    starts_with(buffer, "ERR "))
-		die(_("remote error: %s"), buffer + 4);
 	if ((options & PACKET_READ_CHOMP_NEWLINE) &&
 	    len && buffer[len-1] == '\n')
 	buffer[len] = 0;
 	packet_trace(buffer, len, 0);
+	if ((options & PACKET_READ_DIE_ON_ERR_PACKET) &&
+	    starts_with(buffer, "ERR "))
+		die(_("remote error: %s"), buffer + 4);
 	*pktlen = len;
diff --git a/t/ b/t/
index 747dc4c31d..98ef71b48c 100755
--- a/t/
+++ b/t/
@@ -1241,7 +1241,7 @@ do
 			git fetch ../testrepo/.git $SHA1_2 &&
 			git cat-file commit $SHA1_2 &&
 			test_must_fail git fetch ../testrepo/.git $SHA1_3 2>err &&
-			test_i18ngrep "remote error:.*not our ref" err
+			test_i18ngrep "remote error:.*not our ref.*$SHA1_3\$" err

  parent reply	other threads:[~2019-04-13  5:54 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-13  5:51 [PATCH 0/7] some fetch reachability-error fixes Jeff King
2019-04-13  5:52 ` [PATCH 1/7] t5516: drop ok=sigpipe from unreachable-want tests Jeff King
2019-04-13  5:53 ` [PATCH 2/7] t5530: check protocol response for "not our ref" Jeff King
2019-04-13  5:53 ` [PATCH 3/7] upload-pack: send ERR packet for non-tip objects Jeff King
2019-04-13  5:54 ` Jeff King [this message]
2019-04-13  5:54 ` [PATCH 5/7] fetch: use free_refs() Jeff King
2019-04-13  5:54 ` [PATCH 6/7] remote.c: make singular free_ref() public Jeff King
2019-04-13  5:57 ` [PATCH 7/7] fetch: do not consider peeled tags as advertised tips Jeff King
2019-04-15 21:06 ` [PATCH 0/7] some fetch reachability-error fixes Jonathan Tan

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