[PATCH] arm64: signal: nofpsimd: Do not allocate fp/simd context when not available

[Catalin Marinas]

On Fri, Feb 25, 2022 at 11:40:08AM +0100, David Engraf wrote:
> Commit 6d502b6ba1b2 ("arm64: signal: nofpsimd: Handle fp/simd context for
> signal frames") introduced saving the fp/simd context for signal handling
> only when support is available. But setup_sigframe_layout() always
> reserves memory for fp/simd context. The additional memory is not touched
> because preserve_fpsimd_context() is not called and thus the magic is
> invalid.
> 
> This may lead to an error when parse_user_sigframe() checks the fp/simd
> area and does not find a valid magic number.
> 
> Signed-off-by: David Engraf <david.engraf at sysgo.com>

Given that it's not a regression, I wouldn't push it at -rc7. But if
Will picks it up for 5.18, I think it's worth adding:

Fixes: 6d502b6ba1b2 ("arm64: signal: nofpsimd: Handle fp/simd context for signal frames")
Cc: <stable at vger.kernel.org> # 5.6.x

With that:

Reviewed-by: Catalin Marinas <catalin.marinas at arm.com>