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x86/fpu: Clean up fpregs_set()

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fpregs_set() has unnecessary complexity to support short or nonzero-offset
writes and to handle the case in which a copy from userspace overwrites
some of the target buffer and then fails.  Support for partial writes is
useless -- just require that the write has offset 0 and the correct size,
and copy into a temporary kernel buffer to avoid clobbering the state if
the user access fails.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121452.710467587@linutronix.de
This commit is contained in:
Andy Lutomirski 2021-06-23 14:01:41 +02:00 committed by Borislav Petkov
parent 145e9e0d8c
commit da53f60bb8
1 changed files with 17 additions and 16 deletions
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33
arch/x86/kernel/fpu/regset.c
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@ -304,31 +304,32 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset,
struct user_i387_ia32_struct env;
int ret;
fpu__prepare_write(fpu);
fpstate_sanitize_xstate(fpu);
/* No funny business with partial or oversized writes is permitted. */
if (pos != 0 || count != sizeof(struct user_i387_ia32_struct))
return -EINVAL;
if (!boot_cpu_has(X86_FEATURE_FPU))
if (!cpu_feature_enabled(X86_FEATURE_FPU))
return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
if (!boot_cpu_has(X86_FEATURE_FXSR))
return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
&fpu->state.fsave, 0,
-1);
if (pos > 0 || count < sizeof(env))
convert_from_fxsr(&env, target);
ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
if (!ret)
convert_to_fxsr(&target->thread.fpu.state.fxsave, &env);
if (ret)
return ret;
fpu__prepare_write(fpu);
if (cpu_feature_enabled(X86_FEATURE_FXSR))
convert_to_fxsr(&fpu->state.fxsave, &env);
else
memcpy(&fpu->state.fsave, &env, sizeof(env));
/*
* update the header bit in the xsave header, indicating the
* Update the header bit in the xsave header, indicating the
* presence of FP.
*/
if (boot_cpu_has(X86_FEATURE_XSAVE))
if (cpu_feature_enabled(X86_FEATURE_XSAVE))
fpu->state.xsave.header.xfeatures |= XFEATURE_MASK_FP;
return ret;
return 0;
}
#endif /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */