# CVE-2021-47623: linux: In the Linux kernel, the following vulnerability has been resolved:  powerpc/fixmap: Fix VM debug warning on unmap  U...

CVE-2021-47623 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47623, released July 16, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2021-47623
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0023
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 16, 2024

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.16.10-1 | [DEBIAN-CVE-2021-47623](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47623.md) | Jul 16, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.16.10-1 | [DEBIAN-CVE-2021-47623](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47623.md) | Jul 16, 2024 |
| Linux | linux Debian 14 | 5.16.10-1 | [DEBIAN-CVE-2021-47623](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47623.md) | Jul 16, 2024 |

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