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Message-ID: <2024091109-CVE-2024-45025-94f6@gregkh> Date: Wed, 11 Sep 2024 17:14:21 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-cve-announce@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org> Subject: CVE-2024-45025: fix bitmap corruption on close_range() with CLOSE_RANGE_UNSHARE Description =========== In the Linux kernel, the following vulnerability has been resolved: fix bitmap corruption on close_range() with CLOSE_RANGE_UNSHARE copy_fd_bitmaps(new, old, count) is expected to copy the first count/BITS_PER_LONG bits from old->full_fds_bits[] and fill the rest with zeroes. What it does is copying enough words (BITS_TO_LONGS(count/BITS_PER_LONG)), then memsets the rest. That works fine, *if* all bits past the cutoff point are clear. Otherwise we are risking garbage from the last word we'd copied. For most of the callers that is true - expand_fdtable() has count equal to old->max_fds, so there's no open descriptors past count, let alone fully occupied words in ->open_fds[], which is what bits in ->full_fds_bits[] correspond to. The other caller (dup_fd()) passes sane_fdtable_size(old_fdt, max_fds), which is the smallest multiple of BITS_PER_LONG that covers all opened descriptors below max_fds. In the common case (copying on fork()) max_fds is ~0U, so all opened descriptors will be below it and we are fine, by the same reasons why the call in expand_fdtable() is safe. Unfortunately, there is a case where max_fds is less than that and where we might, indeed, end up with junk in ->full_fds_bits[] - close_range(from, to, CLOSE_RANGE_UNSHARE) with * descriptor table being currently shared * 'to' being above the current capacity of descriptor table * 'from' being just under some chunk of opened descriptors. In that case we end up with observably wrong behaviour - e.g. spawn a child with CLONE_FILES, get all descriptors in range 0..127 open, then close_range(64, ~0U, CLOSE_RANGE_UNSHARE) and watch dup(0) ending up with descriptor #128, despite #64 being observably not open. The minimally invasive fix would be to deal with that in dup_fd(). If this proves to add measurable overhead, we can go that way, but let's try to fix copy_fd_bitmaps() first. * new helper: bitmap_copy_and_expand(to, from, bits_to_copy, size). * make copy_fd_bitmaps() take the bitmap size in words, rather than bits; it's 'count' argument is always a multiple of BITS_PER_LONG, so we are not losing any information, and that way we can use the same helper for all three bitmaps - compiler will see that count is a multiple of BITS_PER_LONG for the large ones, so it'll generate plain memcpy()+memset(). Reproducer added to tools/testing/selftests/core/close_range_test.c The Linux kernel CVE team has assigned CVE-2024-45025 to this issue. Affected and fixed versions =========================== Fixed in 4.19.321 with commit ee501f827f3d Fixed in 5.4.283 with commit e807487a1d5f Fixed in 5.10.225 with commit fe5bf1488170 Fixed in 5.15.166 with commit 5053581fe5df Fixed in 6.1.107 with commit 8cad3b2b3ab8 Fixed in 6.6.48 with commit dd72ae8b0fce Fixed in 6.10.7 with commit c69d18f0ac70 Fixed in 6.11-rc4 with commit 9a2fa1472083 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2024-45025 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: fs/file.c include/linux/bitmap.h tools/testing/selftests/core/close_range_test.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/ee501f827f3db02d4e599afbbc1a7f8b792d05d7 https://git.kernel.org/stable/c/e807487a1d5fd5d941f26578ae826ca815dbfcd6 https://git.kernel.org/stable/c/fe5bf14881701119aeeda7cf685f3c226c7380df https://git.kernel.org/stable/c/5053581fe5dfb09b58c65dd8462bf5dea71f41ff https://git.kernel.org/stable/c/8cad3b2b3ab81ca55f37405ffd1315bcc2948058 https://git.kernel.org/stable/c/dd72ae8b0fce9c0bbe9582b9b50820f0407f8d8a https://git.kernel.org/stable/c/c69d18f0ac7060de724511537810f10f29a27958 https://git.kernel.org/stable/c/9a2fa1472083580b6c66bdaf291f591e1170123a
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