x86/fsgsbase/64: Use TASK_SIZE_MAX for FSBASE/GSBASE upper limits (d696ca01) · Commits · 戴 / test

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:

Andy 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:

Ingo Molnar <mingo@kernel.org>

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);

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