Bugzilla – Bug 1227919
VUL-0: CVE-2021-47623: kernel: powerpc/fixmap: Fix VM debug warning on unmap
Last modified: 2024-07-16 12:59:17 UTC
Description =========== In the Linux kernel, the following vulnerability has been resolved: powerpc/fixmap: Fix VM debug warning on unmap Unmapping a fixmap entry is done by calling __set_fixmap() with FIXMAP_PAGE_CLEAR as flags. Today, powerpc __set_fixmap() calls map_kernel_page(). map_kernel_page() is not happy when called a second time for the same page. WARNING: CPU: 0 PID: 1 at arch/powerpc/mm/pgtable.c:194 set_pte_at+0xc/0x1e8 CPU: 0 PID: 1 Comm: swapper Not tainted 5.16.0-rc3-s3k-dev-01993-g350ff07feb7d-dirty #682 NIP: c0017cd4 LR: c00187f0 CTR: 00000010 REGS: e1011d50 TRAP: 0700 Not tainted (5.16.0-rc3-s3k-dev-01993-g350ff07feb7d-dirty) MSR: 00029032 <EE,ME,IR,DR,RI> CR: 42000208 XER: 00000000 GPR00: c0165fec e1011e10 c14c0000 c0ee2550 ff800000 c0f3d000 00000000 c001686c GPR08: 00001000 b00045a9 00000001 c0f58460 c0f50000 00000000 c0007e10 00000000 GPR16: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 GPR24: 00000000 00000000 c0ee2550 00000000 c0f57000 00000ff8 00000000 ff800000 NIP [c0017cd4] set_pte_at+0xc/0x1e8 LR [c00187f0] map_kernel_page+0x9c/0x100 Call Trace: [e1011e10] [c0736c68] vsnprintf+0x358/0x6c8 (unreliable) [e1011e30] [c0165fec] __set_fixmap+0x30/0x44 [e1011e40] [c0c13bdc] early_iounmap+0x11c/0x170 [e1011e70] [c0c06cb0] ioremap_legacy_serial_console+0x88/0xc0 [e1011e90] [c0c03634] do_one_initcall+0x80/0x178 [e1011ef0] [c0c0385c] kernel_init_freeable+0xb4/0x250 [e1011f20] [c0007e34] kernel_init+0x24/0x140 [e1011f30] [c0016268] ret_from_kernel_thread+0x5c/0x64 Instruction dump: 7fe3fb78 48019689 80010014 7c630034 83e1000c 5463d97e 7c0803a6 38210010 4e800020 81250000 712a0001 41820008 <0fe00000> 9421ffe0 93e1001c 48000030 Implement unmap_kernel_page() which clears an existing pte. The Linux kernel CVE team has assigned CVE-2021-47623 to this issue. Affected and fixed versions =========================== Fixed in 5.10.101 with commit 67baac10dd5a Fixed in 5.15.24 with commit 43ae0ccc4d27 Fixed in 5.16.10 with commit 033fd42c18d9 Fixed in 5.17 with commit aec982603aa8 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-2021-47623 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: arch/powerpc/include/asm/book3s/32/pgtable.h arch/powerpc/include/asm/book3s/64/pgtable.h arch/powerpc/include/asm/fixmap.h arch/powerpc/include/asm/nohash/32/pgtable.h arch/powerpc/include/asm/nohash/64/pgtable.h arch/powerpc/mm/pgtable.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/67baac10dd5ad1e9f50e8f2659984b3b0728d54e https://git.kernel.org/stable/c/43ae0ccc4d2722b833fb59b905af129428e06d03 https://git.kernel.org/stable/c/033fd42c18d9b2121595b6f1e8419a115f9ac5b7 https://git.kernel.org/stable/c/aec982603aa8cc0a21143681feb5f60ecc69d718 References: http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-47623 https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2021/CVE-2021-47623.mbox https://git.kernel.org/stable/c/67baac10dd5ad1e9f50e8f2659984b3b0728d54e https://git.kernel.org/stable/c/43ae0ccc4d2722b833fb59b905af129428e06d03 https://git.kernel.org/stable/c/033fd42c18d9b2121595b6f1e8419a115f9ac5b7 https://git.kernel.org/stable/c/aec982603aa8cc0a21143681feb5f60ecc69d718