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From: Rich Felker <dalias@libc.org>
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Subject: Re: [PATCH v1] mman: fix mmap pass wrong offset to kernel
Date: Mon, 16 Oct 2017 12:27:43 -0400
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On Mon, Oct 16, 2017 at 01:03:18PM +0200, Szabolcs Nagy wrote:
> * Minqiang Chen <ptpt52@gmail.com> [2017-10-16 09:09:32 +0800]:
> > 
> >     musl: fix mmap pass wrong offset to kernel
> > 
> > 
> > 
> >         for example off_t x=0x8d9eb000, the x/4096 result is 0xfff8d9eb,
> > not 0x8d9eb as expecting
> > 
> 
> off_t is 64bit, not 32bit, so x/4096 should not signextend.
> you need to investigate this problem more.

I suspect the calling code stored the offset 0x8d9eb000 in a signed
32-bit variable (converting it to a negative value) and then passed
the resulting negative value to mmap.

Rich