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arm64: ptrace: Avoid setting compat FP[SC]R to garbage if get_user fails 

If get_user() fails when reading the new FPSCR value from userspace
in compat_vfp_get(), then garbage* will be written to the task's
FPSR and FPCR registers.

This patch prevents this by checking the return from get_user()
first.

[*] Actually, zero, due to the behaviour of get_user() on error, but
that's still not what userspace expects.

Fixes: 478fcb2cdb ("arm64: Debugging support")
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Dave Martin 2017-06-29 15:25:47 +01:00 committed by Will Deacon
parent 15ad6ace52
commit 53b1a742ed
1 changed files with 4 additions and 2 deletions
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6
arch/arm64/kernel/ptrace.c
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@ -947,8 +947,10 @@ static int compat_vfp_set(struct task_struct *target,
if (count && !ret) {
ret = get_user(fpscr, (compat_ulong_t *)ubuf);
uregs->fpsr = fpscr & VFP_FPSCR_STAT_MASK;
uregs->fpcr = fpscr & VFP_FPSCR_CTRL_MASK;
if (!ret) {
uregs->fpsr = fpscr & VFP_FPSCR_STAT_MASK;
uregs->fpcr = fpscr & VFP_FPSCR_CTRL_MASK;
}
}
fpsimd_flush_task_state(target);