Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH] futex: Fix fault_in_user_writeable() | Date | Mon, 16 Aug 2021 21:03:18 +0200 |
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On Mon, Aug 16 2021 at 11:27, Davidlohr Bueso wrote: > On Mon, 16 Aug 2021, Huacai Chen wrote: > >>fault_in_user_writeable() should verify R/W access but only verify W. In >>most archs W implies R, but not true in MIPS and LoongArch, so fix it. > > Yuck for a find_vma() in futex.c. If this is a problem in MIPS, shouldn't > the fix be there? Furthermore it's stated that fault_in_user_writeable(): > > "Fault in user address and verify RW access"
That seems to be wishful thinking given the fact that some architectures do not imply R for FLAG_FAULT_WRITE.
> And you guys seem to have proposed it already: > > https://lore.kernel.org/linux-mips/20200630005845.1239974-1-liulichao@loongson.cn/
That's surely one way to fix that. If that does not work for whatever reason, then we really don't want this find_vma() hack there, but rather something like:
if (IS_ENABLED(CONFIG_ARCH_USER_FAULT_VOODOO) && get_user(&tmp, uaddr)) return -EFAULT;
Thanks,
tglx
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