From: Mike Rapoport <rppt@kernel.org>
To: Nam Cao <namcao@linutronix.de>
Cc: "Paul Walmsley" <paul.walmsley@sifive.com>,
"Palmer Dabbelt" <palmer@dabbelt.com>,
"Albert Ou" <aou@eecs.berkeley.edu>,
"Alexandre Ghiti" <alexghiti@rivosinc.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Baoquan He" <bhe@redhat.com>,
"Sami Tolvanen" <samitolvanen@google.com>,
"Chen Jiahao" <chenjiahao16@huawei.com>,
"Björn Töpel" <bjorn@rivosinc.com>,
linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
"Björn Töpel" <bjorn@kernel.org>,
stable@vger.kernel.org
Subject: Re: [PATCH] riscv: fix overlap of allocated page and PTR_ERR
Date: Fri, 26 Apr 2024 08:33:47 +0300 [thread overview]
Message-ID: <Zis8u5qiewKqNzfs@kernel.org> (raw)
In-Reply-To: <20240425115201.3044202-1-namcao@linutronix.de>
On Thu, Apr 25, 2024 at 01:52:01PM +0200, Nam Cao wrote:
> On riscv32, it is possible for the last page in virtual address space
> (0xfffff000) to be allocated. This page overlaps with PTR_ERR, so that
> shouldn't happen.
>
> There is already some code to ensure memblock won't allocate the last page.
> However, buddy allocator is left unchecked.
>
> Fix this by reserving physical memory that would be mapped at virtual
> addresses greater than 0xfffff000.
>
> Reported-by: Björn Töpel <bjorn@kernel.org>
> Closes: https://lore.kernel.org/linux-riscv/878r1ibpdn.fsf@all.your.base.are.belong.to.us
> Fixes: 76d2a0493a17 ("RISC-V: Init and Halt Code")
> Signed-off-by: Nam Cao <namcao@linutronix.de>
> Cc: <stable@vger.kernel.org>
Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>
> ---
> arch/riscv/mm/init.c | 21 +++++++++++----------
> 1 file changed, 11 insertions(+), 10 deletions(-)
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 968761843203..7c985435b3fc 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -235,18 +235,19 @@ static void __init setup_bootmem(void)
> kernel_map.va_pa_offset = PAGE_OFFSET - phys_ram_base;
>
> /*
> - * memblock allocator is not aware of the fact that last 4K bytes of
> - * the addressable memory can not be mapped because of IS_ERR_VALUE
> - * macro. Make sure that last 4k bytes are not usable by memblock
> - * if end of dram is equal to maximum addressable memory. For 64-bit
> - * kernel, this problem can't happen here as the end of the virtual
> - * address space is occupied by the kernel mapping then this check must
> - * be done as soon as the kernel mapping base address is determined.
> + * Reserve physical address space that would be mapped to virtual
> + * addresses greater than (void *)(-PAGE_SIZE) because:
> + * - This memory would overlap with ERR_PTR
> + * - This memory belongs to high memory, which is not supported
> + *
> + * This is not applicable to 64-bit kernel, because virtual addresses
> + * after (void *)(-PAGE_SIZE) are not linearly mapped: they are
> + * occupied by kernel mapping. Also it is unrealistic for high memory
> + * to exist on 64-bit platforms.
> */
> if (!IS_ENABLED(CONFIG_64BIT)) {
> - max_mapped_addr = __pa(~(ulong)0);
> - if (max_mapped_addr == (phys_ram_end - 1))
> - memblock_set_current_limit(max_mapped_addr - 4096);
> + max_mapped_addr = __va_to_pa_nodebug(-PAGE_SIZE);
> + memblock_reserve(max_mapped_addr, (phys_addr_t)-max_mapped_addr);
> }
>
> min_low_pfn = PFN_UP(phys_ram_base);
> --
> 2.39.2
>
--
Sincerely yours,
Mike.
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prev parent reply other threads:[~2024-04-26 5:35 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-25 11:52 [PATCH] riscv: fix overlap of allocated page and PTR_ERR Nam Cao
2024-04-25 12:58 ` Björn Töpel
2024-04-26 5:33 ` Mike Rapoport [this message]
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