CVE - CVE-2021-47640

CVE-ID
CVE-2021-47640	Learn more at National Vulnerability Database (NVD) • CVSS Severity Rating • Fix Information • Vulnerable Software Versions • SCAP Mappings • CPE Information
Description
In the Linux kernel, the following vulnerability has been resolved: powerpc/kasan: Fix early region not updated correctly The shadow's page table is not updated when PTE_RPN_SHIFT is 24 and PAGE_SHIFT is 12. It not only causes false positives but also false negative as shown the following text. Fix it by bringing the logic of kasan_early_shadow_page_entry here. 1. False Positive: ================================================================== BUG: KASAN: vmalloc-out-of-bounds in pcpu_alloc+0x508/0xa50 Write of size 16 at addr f57f3be0 by task swapper/0/1 CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.15.0-12267-gdebe436e77c7 #1 Call Trace: [c80d1c20] [c07fe7b8] dump_stack_lvl+0x4c/0x6c (unreliable) [c80d1c40] [c02ff668] print_address_description.constprop.0+0x88/0x300 [c80d1c70] [c02ff45c] kasan_report+0x1ec/0x200 [c80d1cb0] [c0300b20] kasan_check_range+0x160/0x2f0 [c80d1cc0] [c03018a4] memset+0x34/0x90 [c80d1ce0] [c0280108] pcpu_alloc+0x508/0xa50 [c80d1d40] [c02fd7bc] __kmem_cache_create+0xfc/0x570 [c80d1d70] [c0283d64] kmem_cache_create_usercopy+0x274/0x3e0 [c80d1db0] [c2036580] init_sd+0xc4/0x1d0 [c80d1de0] [c00044a0] do_one_initcall+0xc0/0x33c [c80d1eb0] [c2001624] kernel_init_freeable+0x2c8/0x384 [c80d1ef0] [c0004b14] kernel_init+0x24/0x170 [c80d1f10] [c001b26c] ret_from_kernel_thread+0x5c/0x64 Memory state around the buggy address: f57f3a80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f57f3b00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 >f57f3b80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ^ f57f3c00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f57f3c80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ================================================================== 2. False Negative (with KASAN tests): ================================================================== Before fix: ok 45 - kmalloc_double_kzfree # vmalloc_oob: EXPECTATION FAILED at lib/test_kasan.c:1039 KASAN failure expected in "((volatile char *)area)[3100]", but none occurred not ok 46 - vmalloc_oob not ok 1 - kasan ================================================================== After fix: ok 1 - kasan
References
Note: References are provided for the convenience of the reader to help distinguish between vulnerabilities. The list is not intended to be complete.
MISC:https://git.kernel.org/stable/c/5a3d8f3192a409893c57808cc935e16484df1068 URL:https://git.kernel.org/stable/c/5a3d8f3192a409893c57808cc935e16484df1068 MISC:https://git.kernel.org/stable/c/7f19245c3647afea8c7c41f795506ef70f64b9f2 URL:https://git.kernel.org/stable/c/7f19245c3647afea8c7c41f795506ef70f64b9f2 MISC:https://git.kernel.org/stable/c/dd75080aa8409ce10d50fb58981c6b59bf8707d3 URL:https://git.kernel.org/stable/c/dd75080aa8409ce10d50fb58981c6b59bf8707d3 MISC:https://git.kernel.org/stable/c/de56beace6648065d404cd9835aa7d30e3df519d URL:https://git.kernel.org/stable/c/de56beace6648065d404cd9835aa7d30e3df519d MISC:https://git.kernel.org/stable/c/e3d157a4b4f4e0268c98be5b7013bf4b31234bb6 URL:https://git.kernel.org/stable/c/e3d157a4b4f4e0268c98be5b7013bf4b31234bb6 MISC:https://git.kernel.org/stable/c/f39a3309393a4a484532f6ba745c6acbcfe06115 URL:https://git.kernel.org/stable/c/f39a3309393a4a484532f6ba745c6acbcfe06115
Assigning CNA
kernel.org
Date Record Created
20250226	Disclaimer: The record creation date may reflect when the CVE ID was allocated or reserved, and does not necessarily indicate when this vulnerability was discovered, shared with the affected vendor, publicly disclosed, or updated in CVE.
Phase (Legacy)
Assigned (20250226)
Votes (Legacy)

Comments (Legacy)

Proposed (Legacy)
N/A
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