4ca3c2cf00
This patch moves arm64's struct thread_info from the task stack into task_struct. This protects thread_info from corruption in the case of stack overflows, and makes its address harder to determine if stack addresses are leaked, making a number of attacks more difficult. Precise detection and handling of overflow is left for subsequent patches. Largely, this involves changing code to store the task_struct in sp_el0, and acquire the thread_info from the task struct. Core code now implements current_thread_info(), and as noted in <linux/sched.h> this relies on offsetof(task_struct, thread_info) == 0, enforced by core code. This change means that the 'tsk' register used in entry.S now points to a task_struct, rather than a thread_info as it used to. To make this clear, the TI_* field offsets are renamed to TSK_TI_*, with asm-offsets appropriately updated to account for the structural change. Userspace clobbers sp_el0, and we can no longer restore this from the stack. Instead, the current task is cached in a per-cpu variable that we can safely access from early assembly as interrupts are disabled (and we are thus not preemptible). Both secondary entry and idle are updated to stash the sp and task pointer separately. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Tested-by: Laura Abbott <labbott@redhat.com> Cc: AKASHI Takahiro <takahiro.akashi@linaro.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: James Morse <james.morse@arm.com> Cc: Kees Cook <keescook@chromium.org> Cc: Suzuki K Poulose <suzuki.poulose@arm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> This is a modification of Mark Rutland's original patch. Guards to check if CONFIG_THREAD_INFO_IN_TASK is used has been inserted. get_current() for when CONFIG_THREAD_INFO_IN_TASK is not used has been added to arch/arm64/include/asm/current.h. Bug: 38331309 Change-Id: Ic5eae344a7c2baea0864f6ae16be1e9c60c0a74a (cherry picked from commit c02433dd6de32f042cf3ffe476746b1115b8c096) Signed-off-by: Zubin Mithra <zsm@google.com>
27 lines
510 B
C
27 lines
510 B
C
#ifndef __ASM_CURRENT_H
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#define __ASM_CURRENT_H
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#include <linux/compiler.h>
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#include <asm/sysreg.h>
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#ifndef __ASSEMBLY__
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#ifdef CONFIG_THREAD_INFO_IN_TASK
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struct task_struct;
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static __always_inline struct task_struct *get_current(void)
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{
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return (struct task_struct *)read_sysreg(sp_el0);
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}
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#define current get_current()
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#else
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#include <linux/thread_info.h>
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#define get_current() (current_thread_info()->task)
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#define current get_current()
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#endif
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#endif /* __ASSEMBLY__ */
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#endif /* __ASM_CURRENT_H */
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