Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH] x86/dumpstack: Dump user space code correctly again | Date | Thu, 23 Jul 2020 13:05:43 +0200 |
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Christoph Hellwig <hch@lst.de> writes: > On Wed, Jul 22, 2020 at 07:54:15PM +0200, Thomas Gleixner wrote: >> + /* >> + * Make sure userspace isn't trying to trick us into dumping kernel >> + * memory by pointing the userspace instruction pointer at it. >> + */ >> + if (__chk_range_not_ok(src, nbytes, TASK_SIZE_MAX)) >> + return -EINVAL; >> + >> + return copy_from_user_nmi(buf, (void __user *)src, nbytes); > > copy_from_user_nmi already contains a: > > if (__range_not_ok(from, n, TASK_SIZE)) > return n; > > what is the reason it checks for TASK_SIZE vs TASK_SIZE_MAX, and why > do we need both checks?
TBH, I just kept it because being lazy. But you are right, the check is redundant and TASK_SIZE_MAX is inaccurate as it does not take compat tasks into account. I'll rip that out.
Thanks,
tglx
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