[PATCH] riscv: mmap with PROT_WRITE but no PROT_READ is invalid

[Heinrich Schuchardt]

On 10/6/22 21:17, Eva Kotova wrote:
> On Tue, 31 May 2022 00:56:52 PDT (-0700), coelacanthus at outlook.com wrote:
>  > As mentioned in Table 4.5 in RISC-V spec Volume 2 Section 4.3, write
>  > but not read is "Reserved for future use.". For now, they are not valid.
>  > In the current code, -wx is marked as invalid, but -w- is not marked
>  > as invalid.
> 
> This patch breaks OpenJDK/Java on RISC-V, as it tries to create a w-only 
> protective page:
> 
> #
> # There is insufficient memory for the Java Runtime Environment to 
> continue.
> # Native memory allocation (mmap) failed to map 4096 bytes for failed to 
> allocate memory for PaX check.
> # An error report file with more information is saved as:
> # /root/hs_err_pid107.log
> 
> I bisected to this commit since on Linux 5.19+ java no longer works.
> Perhaps some fallback should be implemented, to prevent userspace 
> breakage. It is currently documented, that at least on i386 PROT_WRITE 
> mappings imply PROT_READ (See man mmap(2) NOTES), this would be a good 
> place to start.

Which test case demonstrates the issue?

Best regards

Heinrich

> 
> Best regards,
> Eva
> 
> _______________________________________________
> linux-riscv mailing list
> linux-riscv at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
>