SQLite: segfault if backup called on closed database

[pdmccormick]

BPO	41815
Nosy	@ambv, @pdmccormick, @miss-islington, @aeros
PRs	bpo-41815: SQLite: segfault if backup called on closed database #22322 [3.9] bpo-41815: SQLite: segfault if backup called on closed database (GH-22322) #22344 [3.8] bpo-41815: SQLite: segfault if backup called on closed database (GH-22322) #22345
Files	fix.patch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2020-09-21.22:07:57.371>
created_at = <Date 2020-09-19.16:08:19.437>
labels = ['3.10', '3.8', '3.9', 'type-crash']
title = 'SQLite: segfault if backup called on closed database'
updated_at = <Date 2020-10-05.16:10:19.853>
user = 'https://github.com/pdmccormick'

bugs.python.org fields:

activity = <Date 2020-10-05.16:10:19.853>
actor = 'lukasz.langa'
assignee = 'none'
closed = True
closed_date = <Date 2020-09-21.22:07:57.371>
closer = 'aeros'
components = []
creation = <Date 2020-09-19.16:08:19.437>
creator = 'pdmccormick'
dependencies = []
files = ['49464']
hgrepos = []
issue_num = 41815
keywords = ['patch']
message_count = 8.0
messages = ['377176', '377201', '377203', '377204', '377287', '377289', '377290', '378052']
nosy_count = 6.0
nosy_names = ['ghaering', 'lukasz.langa', 'python-dev', 'pdmccormick', 'miss-islington', 'aeros']
pr_nums = ['22322', '22344', '22345']
priority = 'normal'
resolution = None
stage = 'commit review'
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue41815'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']

[pdmccormick]

Attempting to backup a closed database will trigger segfault:

target = sqlite.connect(':memory:')
source = sqlite.connect(":memory:")
source.close()
source.backup(target)

[aeros]

With this being a segfault that's simple to replicate under normal circumstances, I've elevated the priority to release blocker. I'll wait on the release manager (Lukasz) for explicit approval for backporting to 3.9 and 3.8, with both branches being in the release candidate phase.

(The attached PR looks to be ready to be merged as well, after a Misc/NEWS entry is added by the author. See #22322 (review) for details.)

[pdmccormick]

Updated sample script, thanks to @aeros for catching the omission:

import sqlite3
target = sqlite3.connect(':memory:')
source = sqlite3.connect(':memory:')
source.close()
source.backup(target)

[miss-islington]

New changeset bfee9fa by Peter McCormick in branch 'master':
bpo-41815: SQLite: segfault if backup called on closed database (GH-22322)
bfee9fa

[miss-islington]

New changeset ca2d99d by Miss Islington (bot) in branch '3.8':
bpo-41815: SQLite: segfault if backup called on closed database (GH-22322)
ca2d99d

[miss-islington]

New changeset 4ee30c4 by Miss Islington (bot) in branch '3.9':
bpo-41815: SQLite: segfault if backup called on closed database (GH-22322)
4ee30c4

[aeros]

I've received approval from Lukasz to backport to 3.9 and 3.8, and have now merged the PRs.

It could use a post-commit review from a core dev that has some additional experience with SQLite3, but it can be de-escalated from release blocker.

[ambv]

New changeset bd55c46 by Łukasz Langa (Miss Islington (bot)) in branch '3.9':
bpo-41815: SQLite: segfault if backup called on closed database (GH-22322)
bd55c46