riscv: signal: fix sigaltstack frame size checking
authorAndy Chiu <andy.chiu@sifive.com>
Tue, 22 Aug 2023 16:49:03 +0000 (16:49 +0000)
committerPalmer Dabbelt <palmer@rivosinc.com>
Thu, 12 Oct 2023 12:38:40 +0000 (05:38 -0700)
commit14a270bfab7ab1c4b605c01eeca5557447ad5a2b
tree0675d3287c023bfe1afefbb1f68ec8740d21de27
parent5abb5c3cd4b38ec32c38a852c83ea04255cecf25
riscv: signal: fix sigaltstack frame size checking

The alternative stack checking in get_sigframe introduced by the Vector
support is not needed and has a problem. It is not needed as we have
already validate it at the beginning of the function if we are already
on an altstack. If not, the size of an altstack is always validated at
its allocation stage with sigaltstack_size_valid().

Besides, we must only regard the size of an altstack if the handler of a
signal is registered with SA_ONSTACK. So, blindly checking overflow of
an altstack if sas_ss_size not equals to zero will check against wrong
signal handlers if only a subset of signals are registered with
SA_ONSTACK.

Fixes: 8ee0b41898fa ("riscv: signal: Add sigcontext save/restore for vector")
Reported-by: Prashanth Swaminathan <prashanthsw@google.com>
Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Link: https://lore.kernel.org/r/20230822164904.21660-1-andy.chiu@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
arch/riscv/kernel/signal.c