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From: "SZEDER Gábor" <szeder.dev@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: "Duy Nguyen" <pclouds@gmail.com>,
	"Thomas Gummerer" <t.gummerer@gmail.com>,
	"Ævar Arnfjörð Bjarmason" <avarab@gmail.com>,
	"Paul-Sebastian Ungureanu" <ungureanupaulsebastian@gmail.com>,
	git@vger.kernel.org, "SZEDER Gábor" <szeder.dev@gmail.com>
Subject: [PATCH 7/6] split-index: BUG() when cache entry refers to non-existing shared entry
Date: Thu, 11 Oct 2018 11:53:57 +0200	[thread overview]
Message-ID: <20181011095357.19061-1-szeder.dev@gmail.com> (raw)
In-Reply-To: <20181011094309.18626-1-szeder.dev@gmail.com>

When the split index feature is in use, then a cache entry is:

  - either only present in the split index, in which case its 'index'
    field must be 0,

  - or it should refer to an existing entry in the shared index, i.e.
    the 'index' field can't be greater than the size of the shared
    index.

If a cache entry were to refer to a non-existing entry in the shared
index, then that's a sign of something being wrong in the index state,
either as a result of a bug in dealing with the split/shared index
entries, or perhaps a (potentially unrelated) memory corruption issue.

prepare_to_write_split_index() already has a condition to catch cache
entries with such bogus 'index' field, but instead of calling BUG() it
just sets cache entry's 'index = 0', and the entry will then be
written to the new split index.

Don't write a new index file from bogus index state, and call BUG()
upon encountering an cache entry referring to a non-existing shared
index entry.

Running the test suite repeatedly with 'GIT_TEST_SPLIT_INDEX=yes'
doesn't trigger this condition.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
---

A follow-up to:

  https://public-inbox.org/git/20180927134324.GI27036@localhost/


 split-index.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/split-index.c b/split-index.c
index 875f538802..5820412dc5 100644
--- a/split-index.c
+++ b/split-index.c
@@ -254,8 +254,8 @@ void prepare_to_write_split_index(struct index_state *istate)
 				continue;
 			}
 			if (ce->index > si->base->cache_nr) {
-				ce->index = 0;
-				continue;
+				BUG("ce refers to a shared ce at %d, which is beyond the shared index size %d",
+				    ce->index, si->base->cache_nr);
 			}
 			ce->ce_flags |= CE_MATCHED; /* or "shared" */
 			base = si->base->cache[ce->index - 1];
-- 
2.19.1.465.gaff195083f


  parent reply	other threads:[~2018-10-11  9:54 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-27 12:44 [PATCH v2 0/5] Fix the racy split index problem SZEDER Gábor
2018-09-27 12:44 ` [PATCH v2 1/5] split-index: add tests to demonstrate " SZEDER Gábor
2018-09-28  0:48   ` SZEDER Gábor
2018-09-28  2:40     ` SZEDER Gábor
2018-09-28 17:30     ` Junio C Hamano
2018-09-27 12:44 ` [PATCH v2 2/5] t1700-split-index: date back files to avoid racy situations SZEDER Gábor
2018-09-27 12:44 ` [PATCH v2 3/5] split-index: count the number of deleted entries SZEDER Gábor
2018-09-27 12:44 ` [PATCH v2 4/5] split-index: don't compare stat data of entries already marked for split index SZEDER Gábor
2018-09-27 13:43   ` SZEDER Gábor
2018-09-27 12:44 ` [PATCH v2 5/5] split-index: smudge and add racily clean cache entries to " SZEDER Gábor
2018-09-27 13:53 ` [PATCH v2 0/5] Fix the racy split index problem Ævar Arnfjörð Bjarmason
2018-09-27 14:23   ` SZEDER Gábor
2018-09-27 15:25     ` Ævar Arnfjörð Bjarmason
2018-09-28  6:57       ` Ævar Arnfjörð Bjarmason
2018-09-28 10:17         ` SZEDER Gábor
2018-10-08 14:54         ` Ævar Arnfjörð Bjarmason
2018-10-08 15:41           ` SZEDER Gábor
2018-09-28 16:24 ` [PATCH v3 0/6] " SZEDER Gábor
2018-09-28 16:24   ` [PATCH v3 1/6] t1700-split-index: document why FSMONITOR is disabled in this test script SZEDER Gábor
2018-09-28 16:24   ` [PATCH v3 2/6] split-index: add tests to demonstrate the racy split index problem SZEDER Gábor
2018-09-28 16:24   ` [PATCH v3 3/6] t1700-split-index: date back files to avoid racy situations SZEDER Gábor
2018-09-28 16:24   ` [PATCH v3 4/6] split-index: count the number of deleted entries SZEDER Gábor
2018-09-28 16:24   ` [PATCH v3 5/6] split-index: don't compare stat data of entries already marked for split index SZEDER Gábor
2018-09-29  5:36     ` Duy Nguyen
2018-09-29  9:14       ` SZEDER Gábor
2018-09-29 10:07         ` SZEDER Gábor
2018-09-28 16:24   ` [PATCH v3 6/6] split-index: smudge and add racily clean cache entries to " SZEDER Gábor
2018-09-29  5:21     ` Duy Nguyen
2018-09-29  7:57       ` SZEDER Gábor
2018-09-30 14:47   ` [PATCH v3 0/6] Fix the racy split index problem SZEDER Gábor
2018-10-05  6:15     ` Junio C Hamano
2018-10-11  9:43   ` [PATCH v4 " SZEDER Gábor
2018-10-11  9:43     ` [PATCH v4 1/6] t1700-split-index: document why FSMONITOR is disabled in this test script SZEDER Gábor
2018-10-11  9:43     ` [PATCH v4 2/6] split-index: add tests to demonstrate the racy split index problem SZEDER Gábor
2018-10-11  9:43     ` [PATCH v4 3/6] t1700-split-index: date back files to avoid racy situations SZEDER Gábor
2018-10-11  9:43     ` [PATCH v4 4/6] split-index: count the number of deleted entries SZEDER Gábor
2018-10-11  9:43     ` [PATCH v4 5/6] split-index: don't compare cached data of entries already marked for split index SZEDER Gábor
2018-10-11  9:43     ` [PATCH v4 6/6] split-index: smudge and add racily clean cache entries to " SZEDER Gábor
2018-10-11  9:53     ` SZEDER Gábor [this message]
2018-10-11 10:36     ` [PATCH v4 0/6] Fix the racy split index problem Ævar Arnfjörð Bjarmason
2018-10-11 11:38       ` SZEDER Gábor
2018-10-12  3:20       ` Junio C Hamano

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