linux-kernel - [PATCH v2 0/2] arm64/mm: prevent panic on -ENOMEM in arch_add

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251013080220.2027757-1-linu.cherian@arm.com>
Date: Mon, 13 Oct 2025 13:32:18 +0530
From: Linu Cherian <linu.cherian@....com>
To: Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ryan Roberts <ryan.roberts@....com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Cc: Anshuman Khandual <anshuman.khandual@....com>,
	Kevin Brodsky <kevin.brodsky@....com>,
	Zhenhua Huang <quic_zhenhuah@...cinc.com>,
	Dev Jain <dev.jain@....com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Yang Shi <yang@...amperecomputing.com>,
	Linu Cherian <linu.cherian@....com>
Subject: [PATCH v2 0/2] arm64/mm: prevent panic on -ENOMEM in arch_add_memory()

arch_add_memory() acts as a means to hotplug memory into a system. It
invokes __create_pgd_mapping() which further unwinds to call
pgtable_alloc(). Initially, this path was only invoked during early boot
and therefore it made sense to BUG_ON() in case pgtable_alloc() failed.
Now however, we risk running into a kernel crash if we try to hotplug
memory into a system that is already extremely tight on available
memory. This is undesirable and hence __create_pgd_mapping() and it's
helpers are reworked to be able to propagate the error from
pgtable_alloc() allowing the system to fail gracefully.

Keeping in mind that it is still essential to BUG_ON()/panic if
pgtable_alloc() encounters failure at the time of boot, a wrapper is
created around __create_pgd_mapping() which is designed to panic() if
it encounters a non-zero return value. This wrapper is then invoked from
the init functions instead of __create_pgd_mapping(), thereby keeping the
original functionality intact.

This theoretical bug was identified by Ryan Roberts<ryan.roberts@....com>
as a part of code review of the following series[1].

[1] https://lore.kernel.org/linux-arm-kernel/20250304222018.615808-4-yang@os.amperecomputing.com/

Changelog

v2:
* With cleanup merged as part of, "arm64: mm: Move KPTI helpers to mmu.c"
  changes in patch 2(v1) got much simplified and squashed to patch 1 itself.
* Patch 2 now does a trivial renaming for better readability 
* Make use of INVALID_PHYS_ADDR for error checks instead of 0.  
* Do early function return where we do not have any
  common cleanup in return path
* Remove redundant variable initialization
* Changed BUG_ON to panic
* Renamed ___create_pgd_mapping to early_create_pgd_mapping  

This series is now rebased to linux-6.18-rc1.

I will be taking the stewardship for this patch series, as Chaitanya
has left Arm.

Thanks,
Linu Cherian.

Chaitanya S Prakash (1):
  arm64/mm: Allow __create_pgd_mapping() to propagate pgtable_alloc()
    errors

Linu Cherian (1):
  arm64/mm: Rename try_pgd_pgtable_alloc_init_mm

 arch/arm64/mm/mmu.c | 208 ++++++++++++++++++++++++++++----------------
 1 file changed, 132 insertions(+), 76 deletions(-)

-- 
2.43.0