The following commit has been merged into the x86/fpu branch of tip: Commit-ID: da53f60bb86e60830932926cf1093953a811912c Gitweb: https://git.kernel.org/tip/da53f60bb86e60830932926cf1093953a811912c Author: Andy Lutomirski <luto@xxxxxxxxxx> AuthorDate: Wed, 23 Jun 2021 14:01:41 +02:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Wed, 23 Jun 2021 17:49:46 +02:00 x86/fpu: Clean up fpregs_set() 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@xxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Reviewed-by: Borislav Petkov <bp@xxxxxxx> Link: https://lkml.kernel.org/r/20210623121452.710467587@xxxxxxxxxxxxx --- arch/x86/kernel/fpu/regset.c | 31 ++++++++++++++++--------------- 1 file changed, 16 insertions(+), 15 deletions(-) diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c index 5610f77..7041b14 100644 --- a/arch/x86/kernel/fpu/regset.c +++ b/arch/x86/kernel/fpu/regset.c @@ -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); + ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1); + if (ret) + return ret; - if (pos > 0 || count < sizeof(env)) - convert_from_fxsr(&env, target); + fpu__prepare_write(fpu); - ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1); - if (!ret) - convert_to_fxsr(&target->thread.fpu.state.fxsave, &env); + 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 */
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