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19 lines
1.9 KiB
Markdown
19 lines
1.9 KiB
Markdown
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### [CVE-2024-56759](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-56759)
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### Description
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In the Linux kernel, the following vulnerability has been resolved:btrfs: fix use-after-free when COWing tree bock and tracing is enabledWhen a COWing a tree block, at btrfs_cow_block(), and we have thetracepoint trace_btrfs_cow_block() enabled and preemption is also enabled(CONFIG_PREEMPT=y), we can trigger a use-after-free in the COWed extentbuffer while inside the tracepoint code. This is because in some pathsthat call btrfs_cow_block(), such as btrfs_search_slot(), we are holdingthe last reference on the extent buffer @buf so btrfs_force_cow_block()drops the last reference on the @buf extent buffer when it callsfree_extent_buffer_stale(buf), which schedules the release of the extentbuffer with RCU. This means that if we are on a kernel with preemption,the current task may be preempted before calling trace_btrfs_cow_block()and the extent buffer already released by the time trace_btrfs_cow_block()is called, resulting in a use-after-free.Fix this by moving the trace_btrfs_cow_block() from btrfs_cow_block() tobtrfs_force_cow_block() before the COWed extent buffer is freed.This also has a side effect of invoking the tracepoint in the tree defragcode, at defrag.c:btrfs_realloc_node(), since btrfs_force_cow_block() iscalled there, but this is fine and it was actually missing there.
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### POC
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#### Reference
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No PoCs from references.
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#### Github
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- https://github.com/bygregonline/devsec-fastapi-report
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- https://github.com/oogasawa/Utility-security
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