Bug 2425151 (CVE-2022-50743)

Summary: CVE-2022-50743 kernel: Linux kernel: Denial of Service in erofs due to memory leak
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in the Linux kernel's erofs filesystem. A local user can trigger a memory leak by exploiting a condition in the `z_erofs_register_pcluster()` function where a pcluster's block address is zero, leading to an unreleased reference count. This vulnerability can result in resource exhaustion, causing a Denial of Service (DoS) on the system.
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Description OSIDB Bzimport 2025-12-24 14:06:45 UTC 
In the Linux kernel, the following vulnerability has been resolved:

erofs: Fix pcluster memleak when its block address is zero

syzkaller reported a memleak:
https://syzkaller.appspot.com/bug?id=62f37ff612f0021641eda5b17f056f1668aa9aed

unreferenced object 0xffff88811009c7f8 (size 136):
  ...
  backtrace:
    [<ffffffff821db19b>] z_erofs_do_read_page+0x99b/0x1740
    [<ffffffff821dee9e>] z_erofs_readahead+0x24e/0x580
    [<ffffffff814bc0d6>] read_pages+0x86/0x3d0
    ...

syzkaller constructed a case: in z_erofs_register_pcluster(),
ztailpacking = false and map->m_pa = zero. This makes pcl->obj.index be
zero although pcl is not a inline pcluster.

Then following path adds refcount for grp, but the refcount won't be put
because pcl is inline.

z_erofs_readahead()
  z_erofs_do_read_page() # for another page
    z_erofs_collector_begin()
      erofs_find_workgroup()
        erofs_workgroup_get()

Since it's illegal for the block address of a non-inlined pcluster to
be zero, add check here to avoid registering the pcluster which would
be leaked.
Comment 1 Alexander B 2025-12-24 22:49:01 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025122449-CVE-2022-50743-8e63@gregkh/T