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Commit d696ca01 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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x86/fsgsbase/64: Use TASK_SIZE_MAX for FSBASE/GSBASE upper limits 



The GSBASE upper limit exists to prevent user code from confusing
the paranoid idtentry path.  The FSBASE upper limit is just for
consistency.  There's no need to enforce a smaller limit for 32-bit
tasks.

Just use TASK_SIZE_MAX.  This simplifies the logic and will save a
few bytes of code.

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/5357f2fe0f103eabf005773b70722451eab09a89.1462897104.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 06cd3d8c

arch/x86/kernel/process_64.c

+2 −2
Original line number Diff line number Diff line
@@ -532,7 +532,7 @@ long do_arch_prctl(struct task_struct *task, int code, unsigned long addr) 


	switch (code) {

	case ARCH_SET_GS:

		if (addr >= TASK_SIZE_OF(task))

		if (addr >= TASK_SIZE_MAX)

			return -EPERM;

		cpu = get_cpu();

		task->thread.gsindex = 0;
@@ -546,7 +546,7 @@ long do_arch_prctl(struct task_struct *task, int code, unsigned long addr) 
	case ARCH_SET_FS:

		/* Not strictly needed for fs, but do it for symmetry

		   with gs */

		if (addr >= TASK_SIZE_OF(task))

		if (addr >= TASK_SIZE_MAX)

			return -EPERM;

		cpu = get_cpu();

		task->thread.fsindex = 0;

arch/x86/kernel/ptrace.c

+2 −2
Original line number Diff line number Diff line
@@ -392,7 +392,7 @@ static int putreg(struct task_struct *child, 


#ifdef CONFIG_X86_64

	case offsetof(struct user_regs_struct,fs_base):

		if (value >= TASK_SIZE_OF(child))

		if (value >= TASK_SIZE_MAX)

			return -EIO;

		/*

		 * When changing the segment base, use do_arch_prctl
@@ -406,7 +406,7 @@ static int putreg(struct task_struct *child, 
		/*

		 * Exactly the same here as the %fs handling above.

		 */

		if (value >= TASK_SIZE_OF(child))

		if (value >= TASK_SIZE_MAX)

			return -EIO;

		if (child->thread.gsbase != value)

			return do_arch_prctl(child, ARCH_SET_GS, value);