osd/ECExtentCache: prevent use-after-free by checking Object existence#64062
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osd/ECExtentCache: prevent use-after-free by checking Object existence#64062
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please see the attached report from ASan: |
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@aainscow hi Alex, could you please help review this change? |
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Jun 20, 2025
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Requesting changes for now, happy to have a discussion on this.
| delete_maybe(); | ||
| if (pg.objects.contains(oid)) { | ||
| delete_maybe(); | ||
| } |
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I have a fix for this in #63873. You don't need the if clause, it is good enough to simply delete the delete_maybe() as the delete always happens at a higher level.
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@aainscow as i explained in details in the commit message, we have to check for its existence. otherwise i still have the use-after-free failure.
regarding removing the delete_maybe(), i tried. but it failed a test. some object was not removed at the end of test.
i will paste the error messages from the failing test once i have access to my linux box.
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@aainscow this is the failing test if we drop delete_maybe() call in unpin().
226: [ RUN ] ECExtentCache.test_invalidate
226: /home/kefu/dev/ceph/src/osd/ECExtentCache.cc: In function 'void ECExtentCache::on_change2() const' thread 7f3e21c00200 time 2025-06-21T06:43:37.436513+0800
226: /home/kefu/dev/ceph/src/osd/ECExtentCache.cc: 335: FAILED ceph_assert(objects.empty())
226: ceph version Development (no_version) tentacle (dev - Debug)
226: 1: (ceph::ClibBackTrace::ClibBackTrace(int)+0x121) [0x7f3e1f4626b9]
226: 2: (ceph::__ceph_assert_fail(char const*, char const*, int, char const*)+0x443) [0x7f3e1f45dc85]
226: 3: (ECExtentCache::on_change2() const+0x76) [0x55a174bc9550]
226: 4: (ECExtentCache_test_invalidate_Test::TestBody()+0x1f0a) [0x55a174a8950e]
226: 5: (void testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*)+0xa4) [0x55a174b8e8be]
226: 6: (void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*)+0xfe) [0x55a174b79bd5]
226: 7: (testing::Test::Run()+0x173) [0x55a174b25ca3]
226: 8: (testing::TestInfo::Run()+0x396) [0x55a174b27202]
226: 9: (testing::TestSuite::Run()+0x367) [0x55a174b283ab]
226: 10: (testing::internal::UnitTestImpl::RunAllTests()+0x8c8) [0x55a174b4980e]
226: 11: (bool testing::internal::HandleSehExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*)+0xa4) [0x55a174b92839]
226: 12: (bool testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>(testing::internal::UnitTestImpl*, bool (testing::internal::UnitTestImpl::*)(), char const*)+0xfe) [0x55a174b7c7b1]
226: 13: (testing::UnitTest::Run()+0x178) [0x55a174b46058]
226: 14: (RUN_ALL_TESTS()+0x11) [0x55a174acfae3]
226: 15: main()
226: 16: /usr/lib/libc.so.6(+0x276b5) [0x7f3e1c8376b5]
226: 17: __libc_start_main()
226: 18: _start()
2/2 Test #226: unittest_extent_cache ............Subprocess aborted***Exception: 0.09 sec
or, probably what you suggest was to remove it from Object::erase_line() ?
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Thanks. I am investigating the failure on my branch.
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I don't get this same failure in my branch, which does contain other fixes to the extent cache. You may well be hitting another failure.
I ran valgrind against the same test you were running and I don't see any use-after-free errors in my code anymore.
Can we wait until my PR has gone in and address this then?
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I don't get this same failure in my branch, which does contain other fixes to the extent cache. You may well be hitting another failure.
I ran valgrind against the same test you were running and I don't see any use-after-free errors in my code anymore.
i am using ASan. probably, as you suggest, some other fixes already address it.
Can we wait until my PR has gone in and address this then?
sure. this PR is not a blocker at this moment. #56537 is pending on some other PRs as well.
Prevent use-after-free errors when clearing cache lines by preserving member variables and verifying Object existence before cleanup. When clearing the last cache line referencing an Object, the Object may be automatically removed from the cache and deleted. Calling delete_maybe() on a deleted Object would result in a use-after-free error. This change: - Preserves necessary member variables on the stack before lines.clear() - Queries the cache with the Object's oid to check it still exists - Only calls delete_maybe() if the Object is still present in cache This ensures safe cleanup by avoiding operations on potentially deleted Objects while maintaining proper cache management. Signed-off-by: Kefu Chai <tchaikov@gmail.com>
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closing in favor of #63873. |
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Prevent use-after-free errors when clearing cache lines by preserving member variables and verifying Object existence before cleanup.
When clearing the last cache line referencing an Object, the Object may be automatically removed from the cache and deleted. Calling delete_maybe() on a deleted Object would result in a use-after-free error.
This change:
This ensures safe cleanup by avoiding operations on potentially deleted Objects while maintaining proper cache management.
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