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CVE PROGRAM SOURCE RECORD7.1 High

CVE-2024-50182

secretmem: disable memfd_secret() if arch cannot set direct map

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Status
Published
Published
Updated
Assigning organization
Linux

Description

In the Linux kernel, the following vulnerability has been resolved: secretmem: disable memfd_secret() if arch cannot set direct map Return -ENOSYS from memfd_secret() syscall if !can_set_direct_map(). This is the case for example on some arm64 configurations, where marking 4k PTEs in the direct map not present can only be done if the direct map is set up at 4k granularity in the first place (as ARM's break-before-make semantics do not easily allow breaking apart large/gigantic pages). More precisely, on arm64 systems with !can_set_direct_map(), set_direct_map_invalid_noflush() is a no-op, however it returns success (0) instead of an error. This means that memfd_secret will seemingly "work" (e.g. syscall succeeds, you can mmap the fd and fault in pages), but it does not actually achieve its goal of removing its memory from the direct map. Note that with this patch, memfd_secret() will start erroring on systems where can_set_direct_map() returns false (arm64 with CONFIG_RODATA_FULL_DEFAULT_ENABLED=n, CONFIG_DEBUG_PAGEALLOC=n and CONFIG_KFENCE=n), but that still seems better than the current silent failure. Since CONFIG_RODATA_FULL_DEFAULT_ENABLED defaults to 'y', most arm64 systems actually have a working memfd_secret() and aren't be affected. From going through the iterations of the original memfd_secret patch series, it seems that disabling the syscall in these scenarios was the intended behavior [1] (preferred over having set_direct_map_invalid_noflush return an error as that would result in SIGBUSes at page-fault time), however the check for it got dropped between v16 [2] and v17 [3], when secretmem moved away from CMA allocations. [1]: https://lore.kernel.org/lkml/20201124164930.GK8537@kernel.org/ [2]: https://lore.kernel.org/lkml/20210121122723.3446-11-rppt@kernel.org/#t [3]: https://lore.kernel.org/lkml/20201125092208.12544-10-rppt@kernel.org/

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 1507f51255c9ff07d75909a84e7c0d7f3c4b2f49 to < d0ae6ffa1aeb297aef89f49cfb894a83c329ebadaffected
  • 1507f51255c9ff07d75909a84e7c0d7f3c4b2f49 to < 5ea0b7af38754d2b45ead9257bca47e84662e926affected
  • 1507f51255c9ff07d75909a84e7c0d7f3c4b2f49 to < 7caf966390e6e4ebf42775df54e7ee1f280ce677affected
  • 1507f51255c9ff07d75909a84e7c0d7f3c4b2f49 to < 757786abe4547eb3d9d0e8350a63bdb0f9824af2affected
  • 1507f51255c9ff07d75909a84e7c0d7f3c4b2f49 to < 532b53cebe58f34ce1c0f34d866f5c0e335c53c6affected

Linux Linux

Default version status: affected

  • 5.14affected
  • 0 to < 5.14unaffected
  • 5.15.169 to ≤ 5.15.*unaffected
  • 6.1.113 to ≤ 6.1.*unaffected
  • 6.6.57 to ≤ 6.6.*unaffected
  • 6.11.4 to ≤ 6.11.*unaffected
  • 6.12 to ≤ *unaffected

References