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x86/fsgsbase/64: Use TASK_SIZE_MAX for FSBASE/GSBASE upper limits

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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>
This commit is contained in:
Andy Lutomirski 2016-05-10 09:18:46 -07:00 committed by Ingo Molnar
parent 06cd3d8c14
commit d696ca016d
2 changed files with 4 additions and 4 deletions
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4
arch/x86/kernel/process_64.c
View file

@ -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;

4
arch/x86/kernel/ptrace.c
View file

@ -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);