8302218: CHeapBitMap::free frees with incorrect size #14079

quadhier · 2023-05-22T12:04:58Z

This patch should fix JDK-8302218.

In destructor of CHeapBitMap, it invokes free() to free allocated memory:

jdk/src/hotspot/share/utilities/bitMap.cpp

Lines 133 to 135 in b3cb82b

    
           CHeapBitMap::~CHeapBitMap() { 
        
             free(map(), size()); 
        
           }

free()'s argument should be size in words, according to:

jdk/src/hotspot/share/utilities/bitMap.cpp

Lines 141 to 143 in b3cb82b

    
           void CHeapBitMap::free(bm_word_t* map, idx_t size_in_words) const { 
        
             ArrayAllocator<bm_word_t>::free(map, size_in_words); 
        
           }

But the destructor pass the argument of size() (which returns _size). It is "size in bits" according to

jdk/src/hotspot/share/utilities/bitMap.hpp

Lines 63 to 65 in b3cb82b

    
           private: 
        
            bm_word_t* _map;     // First word in bitmap 
        
            idx_t      _size;    // Size of bitmap (in bits)

Instead, it should use the return value of size_in_words() to invoke free().

Once ArrayAllocatorMallocLimit option is set, munmap() may be used by free(), which does use the size argument and this may cause crash.

I have tested this patch for tier 1-3 on x86-64 linux.

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Issue

JDK-8302218: CHeapBitMap::free frees with incorrect size

Reviewers

Axel Boldt-Christmas (@xmas92 - Committer)
Ioi Lam (@iklam - Reviewer)
Thomas Schatzl (@tschatzl - Reviewer)

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$ git pr checkout 14079

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bridgekeeper · 2023-05-22T12:05:50Z

👋 Welcome back quadhier! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2023-05-22T12:08:16Z

@quadhier The following label will be automatically applied to this pull request:

hotspot

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

mlbridge · 2023-05-22T12:11:55Z

Webrevs

00: Full (bb9a90b2)

quadhier · 2023-05-22T12:12:58Z

/label remove hotspot
/label add hotspot-runtime

openjdk · 2023-05-22T12:13:59Z

@quadhier
The hotspot label was successfully removed.

openjdk · 2023-05-22T12:15:19Z

@quadhier
The hotspot-runtime label was successfully added.

xmas92

Fix looks good.

Wonder if there is any value in adding a test which lowers ArrayAllocatorMallocLimit to verify that this is working, and that the bug is not reintroduced.

quadhier · 2023-05-22T13:56:37Z

Thanks for your review @xmas92.

Wonder if there is any value in adding a test which lowers ArrayAllocatorMallocLimit to verify that this is working, and that the bug is not reintroduced.

IMHO, exploiting this bug to crack VM is a little bit hard. This bug may cause crash because:

size_in_bits is larger than size_in_words, which causes munmap to unmap more memory regions that what is wanted
and following execution may accidentally touch the unmapped regions (this could be hard to trigger)

I think this is a bug that may cause crashes unexpectedly someday and need to be fixed.

openjdk · 2023-05-22T16:06:12Z

⚠️ @quadhier the full name on your profile does not match the author name in this pull requests' HEAD commit. If this pull request gets integrated then the author name from this pull requests' HEAD commit will be used for the resulting commit. If you wish to push a new commit with a different author name, then please run the following commands in a local repository of your personal fork:

$ git checkout fix-8302218
$ git commit --author='Preferred Full Name <you@example.com>' --allow-empty -m 'Update full name'
$ git push

openjdk · 2023-05-22T16:06:17Z

@quadhier This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8302218: CHeapBitMap::free frees with incorrect size

Reviewed-by: aboldtch, iklam, tschatzl

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 11 new commits pushed to the master branch:

3f4cfbd: 8307190: Refactor ref_at methods in Constant Pool
491bdea: 8308458: Windows build failure with disassembler.cpp(792): warning C4267: '=': conversion from 'size_t' to 'int'
b58980b: 8308034: Some CDS tests need to use @requires vm.flagless
29b8d3d: 8307573: Implementation of JEP 449: Deprecate the Windows 32-bit x86 Port for Removal
5fc9b57: 8308276: Change layout API to work with bytes, not bits
91aeb5d: 8287834: Add SymbolLookup::or method
4f88437: 8307908: [ppc] Add failing RTM tests to ProblemList until 8307907 is fixed.
dc30e68: 8308407: libjvm library not reproducibly comparable between vendors
18e2446: 8301381: Verify DTLS 1.0 cannot be negotiated
b3cb82b: 8307311: Timeouts on one macOS 12.6.1 host of two Swing JTableHeader tests
... and 1 more: https://git.openjdk.org/jdk/compare/05e99db466e7ef5c26f089db772a21cb2ca62e93...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@xmas92, @iklam, @tschatzl) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

iklam · 2023-05-22T16:07:25Z

@quadhier Do you actually use ArrayAllocatorMallocLimit in production? According to comments when this flag was added, it was intended for Solaris only, and the flag has remained an experimental option for the past 10 years.

I have filed https://bugs.openjdk.org/browse/JDK-8308575 for removing this flag.

quadhier · 2023-05-22T16:22:56Z

I have filed https://bugs.openjdk.org/browse/JDK-8308575 for removing this flag.

Great, maybe I could also help with it. I don't use this flag in production myself.

quadhier · 2023-05-22T16:25:07Z

Thank you all for your nice reviews! @iklam @xmas92 @tschatzl

quadhier · 2023-05-22T16:26:17Z

/integrate

openjdk · 2023-05-22T16:28:08Z

@quadhier
Your change (at version bb9a90b) is now ready to be sponsored by a Committer.

quadhier · 2023-05-22T16:30:06Z

Hi, @iklam could you please sponsor this change? Thanks in advance!

iklam · 2023-05-22T16:30:22Z

I have filed https://bugs.openjdk.org/browse/JDK-8308575 for removing this flag.

Great, maybe I could also help with it. I don't use this flag in production myself.

Actually there's already a bug filed for the same issue. See https://bugs.openjdk.org/browse/JDK-8299915 and #11931

iklam · 2023-05-22T16:50:20Z

/sponsor

openjdk · 2023-05-22T16:51:25Z

Going to push as commit f99ad11.
Since your change was applied there have been 12 commits pushed to the master branch:

d77a410: 8308388: Update description of SourceVersion.RELEASE_21
3f4cfbd: 8307190: Refactor ref_at methods in Constant Pool
491bdea: 8308458: Windows build failure with disassembler.cpp(792): warning C4267: '=': conversion from 'size_t' to 'int'
b58980b: 8308034: Some CDS tests need to use @requires vm.flagless
29b8d3d: 8307573: Implementation of JEP 449: Deprecate the Windows 32-bit x86 Port for Removal
5fc9b57: 8308276: Change layout API to work with bytes, not bits
91aeb5d: 8287834: Add SymbolLookup::or method
4f88437: 8307908: [ppc] Add failing RTM tests to ProblemList until 8307907 is fixed.
dc30e68: 8308407: libjvm library not reproducibly comparable between vendors
18e2446: 8301381: Verify DTLS 1.0 cannot be negotiated
... and 2 more: https://git.openjdk.org/jdk/compare/05e99db466e7ef5c26f089db772a21cb2ca62e93...master

Your commit was automatically rebased without conflicts.

openjdk · 2023-05-22T16:51:39Z

@iklam @quadhier Pushed as commit f99ad11.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

Fix the bug of freeing incorrect size in CHeapBitMap destructor

bb9a90b

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openjdk bot added the hotspot hotspot-dev@openjdk.org label May 22, 2023

openjdk bot removed the hotspot hotspot-dev@openjdk.org label May 22, 2023

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8302218: CHeapBitMap::free frees with incorrect size #14079

8302218: CHeapBitMap::free frees with incorrect size #14079

quadhier commented May 22, 2023 •

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	void CHeapBitMap::free(bm_word_t* map, idx_t size_in_words) const {
	ArrayAllocator<bm_word_t>::free(map, size_in_words);
	}

	private:
	bm_word_t* _map; // First word in bitmap
	idx_t _size; // Size of bitmap (in bits)

8302218: CHeapBitMap::free frees with incorrect size #14079

8302218: CHeapBitMap::free frees with incorrect size #14079

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