php / php/php-src

pdo_sqlite segmentation fault

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Bug Status: Needs Triage
Dominant language
C
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Avg merge
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Merged PRs (30d)
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Description

Description

The following code:

<?php
$db = Pdo\Sqlite::connect('sqlite::memory:');
$db->exec("CREATE TABLE t(x TEXT)");
$db->exec("INSERT INTO t VALUES ('b'),('a'),('c'),('d'),('e')");

$stmt = null;
$db->createCollation('evil', function ($a, $b) use (&$stmt) {
    $stmt->closeCursor();        
    return $a <=> $b;
});

$stmt = $db->prepare("SELECT x FROM t ORDER BY x COLLATE evil");
$stmt->execute();            

Resulted in this output:


Deprecated: Method PDO::sqliteCreateCollation() is deprecated since 8.5, use Pdo\Sqlite::createCollation() instead in /audit/repro/battery7/e7_06_collation_closecursor.php on line 8
AddressSanitizer:DEADLYSIGNAL
=================================================================
==7==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x000000000000 bp 0xffffe64c9040 sp 0xffffe64c9020 T0)
==7==Hint: pc points to the zero page.
==7==The signal is caused by a READ memory access.
==7==Hint: address points to the zero page.
    #0 0x0  (<unknown module>)
LLVMSymbolizer: error reading file: No such file or directory
    #1 0xffffade2578c  (linux-vdso.so.1+0x78c)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV (<unknown module>) 
==7==ABORTING

gdb backtrace:

#0  0x0000000000000000 in ?? ()
#1  0x... in ?? () from /lib/.../libsqlite3.so.0
#2  0x... in ?? () from /lib/.../libsqlite3.so.0
#3  sqlite3VdbeExec () from libsqlite3.so.0
#4  sqlite3_step () from libsqlite3.so.0
#5  pdo_sqlite_stmt_execute (stmt=...) at ext/pdo_sqlite/sqlite_statement.c:54
#6  zim_PDOStatement_execute (...) at ext/pdo/pdo_stmt.c:456
...
PHP Version
8.6.0-dev
Operating System

Ubuntu 22.04

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the reproducer in the issue and inspect ext/pdo_sqlite/sqlite_statement.c:54, then trace the call through ext/pdo/pdo_stmt.c:456 while the collation callback closes the cursor. Done means the supplied script no longer segfaults under AddressSanitizer and the behavior is covered by an appropriate regression test.

Written by the indexing model from the issue text.

Assessment

Tech stack
php, sqlite
Domain
databases
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Active
Clarity
Mostly clear
Newbie friendliness
48/100

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