Date: Sat, 21 Oct 2017 00:20:05 -0400 From: Rich Felker <dalias@...c.org> To: Minqiang Chen <ptpt52@...il.com> Cc: musl@...ts.openwall.com Subject: Re: [PATCH v1] mman: fix mmap pass wrong offset to kernel On Fri, Oct 20, 2017 at 05:06:29PM +0800, Minqiang Chen wrote: > I don’t know why, but this is how I fix it. > on arm_cortex-a15 it is 32bit arch off_t is always 64-bit regardless of whether it's a 32-bit arch. This is definitely a bug in the calling program, not musl. > > 在 2017年10月17日，00:27，Rich Felker <dalias@...c.org> 写道： > > > > On Mon, Oct 16, 2017 at 01:03:18PM +0200, Szabolcs Nagy wrote: > >> * Minqiang Chen <ptpt52@...il.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 >
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