Messages in this thread | | | Date | Sat, 11 Feb 2017 21:13:01 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCHv4 4/5] x86/mm: check in_compat_syscall() instead TIF_ADDR32 for mmap(MAP_32BIT) |
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On Mon, 30 Jan 2017, Dmitry Safonov wrote:
> At this momet, logic in arch_get_unmapped_area{,_topdown} for mmaps with > MAP_32BIT flag checks TIF_ADDR32 which means: > o if 32-bit ELF changes mode to 64-bit on x86_64 and then tries to > mmap() with MAP_32BIT it'll result in addr over 4Gb (as default is > top-down allocation) > o if 64-bit ELF changes mode to 32-bit and tries mmap() with MAP_32BIT, > it'll allocate only memory in 1GB space: [0x40000000, 0x80000000). > > Fix it by handeling MAP_32BIT in 64-bit syscalls only.
I really have a hard time to understand what is fixed and how that is related to the $subject.
Again. Please explain the problem first properly so one can understand the issue immediately.
> As a little bonus it'll make thread flag a little less used.
I really do not understand the bonus part here. You replace the thread flag check with a different one and AFAICT this looks like oart of the 'fix'.
Thanks,
tglx
> @@ -101,7 +101,7 @@ SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len, > static void find_start_end(unsigned long flags, unsigned long *begin, > unsigned long *end) > { > - if (!test_thread_flag(TIF_ADDR32) && (flags & MAP_32BIT)) { > + if (!in_compat_syscall() && (flags & MAP_32BIT)) { > /* This is usually used needed to map code in small > model, so it needs to be in the first 31bit. Limit > it to that. This means we need to move the > @@ -195,7 +195,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, > return addr; > > /* for MAP_32BIT mappings we force the legacy mmap base */ > - if (!test_thread_flag(TIF_ADDR32) && (flags & MAP_32BIT)) > + if (!in_compat_syscall() && (flags & MAP_32BIT)) > goto bottomup; > > /* requesting a specific address */ > -- > 2.11.0 > >
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