From: Junio C Hamano <gitster@pobox•com>
To: "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail•com>
Cc: git@vger•kernel.org, peff@peff•net, Derrick Stolee <stolee@gmail•com>
Subject: Re: [PATCH 3/3] index-pack: allow revisiting REF_DELTA chains
Date: Thu, 24 Apr 2025 14:41:45 -0700 [thread overview]
Message-ID: <xmqqjz79texy.fsf@gitster.g> (raw)
In-Reply-To: <27d36402fe9c8262c459d606bf4aace1919aa2ae.1745430004.git.gitgitgadget@gmail.com> (Derrick Stolee via GitGitGadget's message of "Wed, 23 Apr 2025 17:40:04 +0000")
"Derrick Stolee via GitGitGadget" <gitgitgadget@gmail•com> writes:
> From: Derrick Stolee <stolee@gmail•com>
>
> As detailed in the previous changes to t5309-pack-delta-cycles.sh, the
> logic within 'git index-pack' to analyze an incoming thin packfile with
> REF_DELTAs is suspect. The algorithm is overly cautious around delta
> cycles, and that leads in fact to failing even when there is no cycle.
>
> This change adjusts the algorithm to no longer fail in these cases. In
> fact, these cycle cases will no longer fail but more importantly the
> valid cases will no longer fail, either. The resulting packfile from the
> --fix-thin operation will not have cycles either since REF_DELTAs are
> forbidden from the on-disk format and OFS_DELTAs are impossible to write
> as a cycle.
Loosening cycle avoidance indeed is worrysome. How do we guarantee
"since REF_DELTAs are forbidden from the on-disk format" (it is
obvious with OFS_DELTA only you cannot form a cycle)? By code
inspection and in-code comment for the code path of "--fix-thin"?
I think the most interesting question would be how, with the
loosening of the cycle check in this patch, we would still protect
against a malicious on-the-wire packdata that has a cycle in it
already, where deltas cannot be resolved.
next prev parent reply other threads:[~2025-04-24 21:41 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-04-23 17:40 [PATCH 0/3] Fix REF_DELTA chain bug in 'git index-pack' Derrick Stolee via GitGitGadget
2025-04-23 17:40 ` [PATCH 1/3] test-tool: add pack-deltas helper Derrick Stolee via GitGitGadget
2025-04-23 19:26 ` Junio C Hamano
2025-04-23 19:32 ` Derrick Stolee
2025-04-24 19:41 ` Junio C Hamano
2025-04-24 20:06 ` Derrick Stolee
2025-04-24 20:56 ` Junio C Hamano
2025-04-25 4:34 ` Patrick Steinhardt
2025-04-25 9:34 ` Johannes Schindelin
2025-04-25 9:45 ` Patrick Steinhardt
2025-04-25 9:51 ` Johannes Schindelin
2025-04-25 16:27 ` Junio C Hamano
2025-04-28 15:22 ` Derrick Stolee
2025-04-28 16:37 ` Junio C Hamano
2025-04-28 18:59 ` Derrick Stolee
2025-04-28 20:35 ` Junio C Hamano
2025-04-23 17:40 ` [PATCH 2/3] t5309: create failing test for 'git index-pack' Derrick Stolee via GitGitGadget
2025-04-23 19:37 ` Junio C Hamano
2025-04-23 17:40 ` [PATCH 3/3] index-pack: allow revisiting REF_DELTA chains Derrick Stolee via GitGitGadget
2025-04-24 21:41 ` Junio C Hamano [this message]
2025-04-25 3:49 ` Derrick Stolee
2025-04-28 20:24 ` [PATCH v2 0/3] Fix REF_DELTA chain bug in 'git index-pack' Derrick Stolee via GitGitGadget
2025-04-28 20:24 ` [PATCH v2 1/3] test-tool: add pack-deltas helper Derrick Stolee via GitGitGadget
2025-04-28 20:24 ` [PATCH v2 2/3] t5309: create failing test for 'git index-pack' Derrick Stolee via GitGitGadget
2025-04-28 20:24 ` [PATCH v2 3/3] index-pack: allow revisiting REF_DELTA chains Derrick Stolee via GitGitGadget
2025-05-07 2:08 ` Taylor Blau
2025-05-07 13:47 ` Derrick Stolee
2025-04-28 22:40 ` [PATCH v2 0/3] Fix REF_DELTA chain bug in 'git index-pack' Junio C Hamano
2025-04-29 5:33 ` Patrick Steinhardt
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