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From: Jeff King <peff@peff.net>
To: git@vger.kernel.org
Cc: Yiyuan guo <yguoaz@gmail.com>
Subject: [PATCH 5/5] pack-objects: clamp negative depth to 0
Date: Sat, 1 May 2021 10:04:34 -0400	[thread overview]
Message-ID: <YI1f8jKReuE3LXVH@coredump.intra.peff.net> (raw)
In-Reply-To: <YI1fbERSuS7Y3LKh@coredump.intra.peff.net>

A negative delta depth makes no sense, and the code is not prepared to
handle it. If passed "--depth=-1" on the command line, then this line
from break_delta_chains():

	cur->depth = (total_depth--) % (depth + 1);

triggers a divide-by-zero. This is undefined behavior according to the C
standard, but on POSIX systems results in SIGFPE killing the process.
This is certainly one way to inform the use that the command was
invalid, but it's a bit friendlier to just treat it as "don't allow any
deltas", which we already do for --depth=0.

Signed-off-by: Jeff King <peff@peff.net>
---
 builtin/pack-objects.c      | 2 ++
 t/t5316-pack-delta-depth.sh | 7 +++++++
 2 files changed, 9 insertions(+)

diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index ea7a5b3ba5..da5e0700f9 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -3861,6 +3861,8 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 	if (pack_to_stdout != !base_name || argc)
 		usage_with_options(pack_usage, pack_objects_options);
 
+	if (depth < 0)
+		depth = 0;
 	if (depth >= (1 << OE_DEPTH_BITS)) {
 		warning(_("delta chain depth %d is too deep, forcing %d"),
 			depth, (1 << OE_DEPTH_BITS) - 1);
diff --git a/t/t5316-pack-delta-depth.sh b/t/t5316-pack-delta-depth.sh
index 3e84df4137..759169d074 100755
--- a/t/t5316-pack-delta-depth.sh
+++ b/t/t5316-pack-delta-depth.sh
@@ -102,4 +102,11 @@ test_expect_success '--depth=0 disables deltas' '
 	test_cmp expect actual
 '
 
+test_expect_success 'negative depth disables deltas' '
+	pack=$(git pack-objects --all --depth=-1 </dev/null pack) &&
+	echo 0 >expect &&
+	max_chain pack-$pack.pack >actual &&
+	test_cmp expect actual
+'
+
 test_done
-- 
2.31.1.875.g5dccece0aa

  parent reply	other threads:[~2021-05-01 14:04 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-01 14:02 [PATCH 0/5] pack-objects: better handling of negative options Jeff King
2021-05-01 14:02 ` [PATCH 1/5] t5300: modernize basic tests Jeff King
2021-05-03  5:27   ` Junio C Hamano
2021-05-03 14:53     ` Jeff King
2021-05-01 14:03 ` [PATCH 2/5] t5300: check that we produced expected number of deltas Jeff King
2021-05-01 14:03 ` [PATCH 3/5] pack-objects: clamp negative window size to 0 Jeff King
2021-05-03 12:10   ` Derrick Stolee
2021-05-03 14:55     ` Jeff King
2021-05-04 18:47       ` René Scharfe
2021-05-04 21:38         ` Jeff King
2021-05-05 11:53         ` Ævar Arnfjörð Bjarmason
2021-05-05 16:19           ` René Scharfe
2021-05-01 14:04 ` [PATCH 4/5] t5316: check behavior of pack-objects --depth=0 Jeff King
2021-05-01 14:04 ` Jeff King [this message]
2021-05-03 12:11   ` [PATCH 5/5] pack-objects: clamp negative depth to 0 Derrick Stolee

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