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/openbmc/linux/include/linux/ |
H A D | signal.h | 1bdda24c Thu Oct 21 17:55:05 CDT 2021 Thomas Gleixner <tglx@linutronix.de> signal: Add an optional check for altstack size
New x86 FPU features will be very large, requiring ~10k of stack in signal handlers. These new features require a new approach called "dynamic features".
The kernel currently tries to ensure that altstacks are reasonably sized. Right now, on x86, sys_sigaltstack() requires a size of >=2k. However, that 2k is a constant. Simply raising that 2k requirement to >10k for the new features would break existing apps which have a compiled-in size of 2k.
Instead of universally enforcing a larger stack, prohibit a process from using dynamic features without properly-sized altstacks. This must be enforced in two places:
* A dynamic feature can not be enabled without an large-enough altstack for each process thread. * Once a dynamic feature is enabled, any request to install a too-small altstack will be rejected
The dynamic feature enabling code must examine each thread in a process to ensure that the altstacks are large enough. Add a new lock (sigaltstack_lock()) to ensure that threads can not race and change their altstack after being examined.
Add the infrastructure in form of a config option and provide empty stubs for architectures which do not need dynamic altstack size checks.
This implementation will be fleshed out for x86 in a future patch called
x86/arch_prctl: Add controls for dynamic XSTATE components
[dhansen: commit message. ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20211021225527.10184-2-chang.seok.bae@intel.com
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/openbmc/linux/arch/ |
H A D | Kconfig | 1bdda24c Thu Oct 21 17:55:05 CDT 2021 Thomas Gleixner <tglx@linutronix.de> signal: Add an optional check for altstack size
New x86 FPU features will be very large, requiring ~10k of stack in signal handlers. These new features require a new approach called "dynamic features".
The kernel currently tries to ensure that altstacks are reasonably sized. Right now, on x86, sys_sigaltstack() requires a size of >=2k. However, that 2k is a constant. Simply raising that 2k requirement to >10k for the new features would break existing apps which have a compiled-in size of 2k.
Instead of universally enforcing a larger stack, prohibit a process from using dynamic features without properly-sized altstacks. This must be enforced in two places:
* A dynamic feature can not be enabled without an large-enough altstack for each process thread. * Once a dynamic feature is enabled, any request to install a too-small altstack will be rejected
The dynamic feature enabling code must examine each thread in a process to ensure that the altstacks are large enough. Add a new lock (sigaltstack_lock()) to ensure that threads can not race and change their altstack after being examined.
Add the infrastructure in form of a config option and provide empty stubs for architectures which do not need dynamic altstack size checks.
This implementation will be fleshed out for x86 in a future patch called
x86/arch_prctl: Add controls for dynamic XSTATE components
[dhansen: commit message. ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20211021225527.10184-2-chang.seok.bae@intel.com
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/openbmc/linux/kernel/ |
H A D | signal.c | 1bdda24c Thu Oct 21 17:55:05 CDT 2021 Thomas Gleixner <tglx@linutronix.de> signal: Add an optional check for altstack size
New x86 FPU features will be very large, requiring ~10k of stack in signal handlers. These new features require a new approach called "dynamic features".
The kernel currently tries to ensure that altstacks are reasonably sized. Right now, on x86, sys_sigaltstack() requires a size of >=2k. However, that 2k is a constant. Simply raising that 2k requirement to >10k for the new features would break existing apps which have a compiled-in size of 2k.
Instead of universally enforcing a larger stack, prohibit a process from using dynamic features without properly-sized altstacks. This must be enforced in two places:
* A dynamic feature can not be enabled without an large-enough altstack for each process thread. * Once a dynamic feature is enabled, any request to install a too-small altstack will be rejected
The dynamic feature enabling code must examine each thread in a process to ensure that the altstacks are large enough. Add a new lock (sigaltstack_lock()) to ensure that threads can not race and change their altstack after being examined.
Add the infrastructure in form of a config option and provide empty stubs for architectures which do not need dynamic altstack size checks.
This implementation will be fleshed out for x86 in a future patch called
x86/arch_prctl: Add controls for dynamic XSTATE components
[dhansen: commit message. ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20211021225527.10184-2-chang.seok.bae@intel.com
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