ACK: [SRU][Xenial][PATCH 0/2] arm64: sigaltstack fails with MINSIGSTKSZ for 32-bit processes (LP: #1844155)

[Stefan Bader]

On 01.10.19 19:56, Juerg Haefliger wrote:
> [Impact]
> 
> The arm64 kernel allows one to run aarch32 processes on an aarch64 processor, using the standard 32/64-bit syscall compatibility. However this compat layer does not correctly validate the arguments of the sigaltstack syscall which can result in process failures.
> 
> [Test Case]
> 
> The simple reproducer from https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=904385 triggers a memory allocation error with the current Xenial 4.4 kernel.
> 
> [Fix]
> 
> Backport the following two upstream commits:
> 24951465cbd2 arm64: compat: Provide definition for COMPAT_SIGMINSTKSZ
> 22839869f21a signal: Introduce COMPAT_SIGMINSTKSZ for use in compat_sys_sigaltstack
> 
> With these two commits, the reproducer no longer fails.
> 
> [Regression Potential]
> 
> Low. The modifications are trivial and the two patches have been in upstream for quite a while.
> 
> Will Deacon (2):
>   signal: Introduce COMPAT_SIGMINSTKSZ for use in compat_sys_sigaltstack
>   arm64: compat: Provide definition for COMPAT_SIGMINSTKSZ
> 
>  arch/arm64/include/asm/compat.h |  1 +
>  include/linux/compat.h          |  3 +++
>  kernel/signal.c                 | 14 +++++++++-----
>  3 files changed, 13 insertions(+), 5 deletions(-)
> 
This looks right from what I remember (one additional function argument and
three call sites to adapt) for the larger patch. And is testable.

Acked-by: Stefan Bader <stefan.bader at canonical.com>

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