diff options
| author | Chang S. Bae <chang.seok.bae@intel.com> | 2018-11-26 11:55:24 -0800 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2018-12-18 14:26:09 +0100 |
| commit | 87ab4689ca6526079ab6f5150219ee88b42000ae (patch) | |
| tree | 585d3e7a0524b541de9a006d015a2ec7bc1984e6 /arch/x86/kernel/ptrace.c | |
| parent | 721066dfd4d5c0fee5772c777d6930d0f423b4eb (diff) | |
x86/fsgsbase/64: Fix the base write helper functions
Andy spotted a regression in the fs/gs base helpers after the patch series
was committed. The helper functions which write fs/gs base are not just
writing the base, they are also changing the index. That's wrong and needs
to be separated because writing the base has not to modify the index.
While the regression is not causing any harm right now because the only
caller depends on that behaviour, it's a guarantee for subtle breakage down
the road.
Make the index explicitly changed from the caller, instead of including
the code in the helpers.
Subsequently, the task write helpers do not handle for the current task
anymore. The range check for a base value is also factored out, to minimize
code redundancy from the caller.
Fixes: b1378a561fd1 ("x86/fsgsbase/64: Introduce FS/GS base helper functions")
Suggested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Link: https://lkml.kernel.org/r/20181126195524.32179-1-chang.seok.bae@intel.com
Diffstat (limited to 'arch/x86/kernel/ptrace.c')
| -rw-r--r-- | arch/x86/kernel/ptrace.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c index ffae9b9740fd..4b8ee05dd6ad 100644 --- a/arch/x86/kernel/ptrace.c +++ b/arch/x86/kernel/ptrace.c @@ -397,11 +397,12 @@ static int putreg(struct task_struct *child, if (value >= TASK_SIZE_MAX) return -EIO; /* - * When changing the FS base, use the same - * mechanism as for do_arch_prctl_64(). + * When changing the FS base, use do_arch_prctl_64() + * to set the index to zero and to set the base + * as requested. */ if (child->thread.fsbase != value) - return x86_fsbase_write_task(child, value); + return do_arch_prctl_64(child, ARCH_SET_FS, value); return 0; case offsetof(struct user_regs_struct,gs_base): /* @@ -410,7 +411,7 @@ static int putreg(struct task_struct *child, if (value >= TASK_SIZE_MAX) return -EIO; if (child->thread.gsbase != value) - return x86_gsbase_write_task(child, value); + return do_arch_prctl_64(child, ARCH_SET_GS, value); return 0; #endif } |