* [PATCH v1] mman: fix mmap pass wrong offset to kernel
@ 2017-10-16 1:09 Minqiang Chen
2017-10-16 11:03 ` Szabolcs Nagy
0 siblings, 1 reply; 4+ messages in thread
From: Minqiang Chen @ 2017-10-16 1:09 UTC (permalink / raw)
To: musl
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Author: Chen Minqiang <ptpt52@gmail.com>
Date: Mon Oct 16 08:57:41 2017 +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
this happens on arm_cortex-a15 with gcc 6.3.x
Signed-off-by: Chen Minqiang <ptpt52@gmail.com>
*diff --git a/src/mman/mmap.c b/src/mman/mmap.c*
*index 1592403..a09c901 100644*
*--- a/src/mman/mmap.c*
*+++ b/src/mman/mmap.c*
*@@ -27,7 +27,7 @@* void *__mmap(void *start, size_t len, int prot, int
flags, int fd, off_t off)
__vm_wait();
}
#ifdef SYS_mmap2
*- ret = __syscall(SYS_mmap2, start, len, prot, flags, fd, off/UNIT);*
*+* *ret = __syscall(SYS_mmap2, start, len, prot, flags, fd,
(unsigned long)off/UNIT);*
#else
ret = __syscall(SYS_mmap, start, len, prot, flags, fd, off);
#endif
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v1] mman: fix mmap pass wrong offset to kernel
2017-10-16 1:09 [PATCH v1] mman: fix mmap pass wrong offset to kernel Minqiang Chen
@ 2017-10-16 11:03 ` Szabolcs Nagy
2017-10-16 16:27 ` Rich Felker
0 siblings, 1 reply; 4+ messages in thread
From: Szabolcs Nagy @ 2017-10-16 11:03 UTC (permalink / raw)
To: Minqiang Chen; +Cc: musl
* 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.
> this happens on arm_cortex-a15 with gcc 6.3.x
>
>
>
> Signed-off-by: Chen Minqiang <ptpt52@gmail.com>
>
>
> *diff --git a/src/mman/mmap.c b/src/mman/mmap.c*
>
> *index 1592403..a09c901 100644*
>
> *--- a/src/mman/mmap.c*
>
> *+++ b/src/mman/mmap.c*
>
> *@@ -27,7 +27,7 @@* void *__mmap(void *start, size_t len, int prot, int
> flags, int fd, off_t off)
>
> __vm_wait();
>
> }
>
> #ifdef SYS_mmap2
>
> *- ret = __syscall(SYS_mmap2, start, len, prot, flags, fd, off/UNIT);*
>
> *+* *ret = __syscall(SYS_mmap2, start, len, prot, flags, fd,
> (unsigned long)off/UNIT);*
this is wrong, off is 64bit signed int, it can have values
outside of the range of unsigned long.
(and your email client ruined the patch with random '*' and '\n')
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v1] mman: fix mmap pass wrong offset to kernel
2017-10-16 11:03 ` Szabolcs Nagy
@ 2017-10-16 16:27 ` Rich Felker
[not found] ` <94E25077-4463-454D-96BF-BA1DA9166F60@gmail.com>
0 siblings, 1 reply; 4+ messages in thread
From: Rich Felker @ 2017-10-16 16:27 UTC (permalink / raw)
To: musl; +Cc: Minqiang Chen
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
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2017-10-21 4:20 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2017-10-16 1:09 [PATCH v1] mman: fix mmap pass wrong offset to kernel Minqiang Chen
2017-10-16 11:03 ` Szabolcs Nagy
2017-10-16 16:27 ` Rich Felker
[not found] ` <94E25077-4463-454D-96BF-BA1DA9166F60@gmail.com>
2017-10-21 4:20 ` Rich Felker
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