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SubjectRe: [PATCH 1/2] fs, elf: drop MAP_FIXED usage from elf_map
On Tue 17-10-17 09:35:57, James Hogan wrote:
> On Tue, Oct 17, 2017 at 09:37:48AM +0200, Michal Hocko wrote:
[...]
> > This would be something like. I wanted to share elf_vm_mmap but didn't
> > find a proper place to not cause include dependency hell so I balied out
> > to c&p.
> > ---
> > diff --git a/arch/metag/kernel/process.c b/arch/metag/kernel/process.c
> > index c4606ce743d2..b20596b4c4c2 100644
> > --- a/arch/metag/kernel/process.c
> > +++ b/arch/metag/kernel/process.c
> > @@ -378,6 +378,29 @@ int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
> >
> > #define BAD_ADDR(x) ((unsigned long)(x) >= TASK_SIZE)
> >
> > +static unsigned long elf_vm_mmap(struct file *filep, unsigned long addr,
> > + unsigned long size, int prot, int type, unsigned long off)
> > +{
> > + unsigned long map_addr;
> > +
> > + /*
> > + * If caller requests the mapping at a specific place, make sure we fail
> > + * rather than potentially clobber an existing mapping which can have
> > + * security consequences (e.g. smash over the stack area).
> > + */
> > + map_addr = vm_mmap(filep, addr, size, prot, type & ~MAP_FIXED, off);
> > + if (BAD_ADDR(map_addr))
> > + return map_addr;
> > +
> > + if ((type & MAP_FIXED) && map_addr != addr) {
> > + pr_info("Uhuuh, elf segement at %p requested but the memory is mapped already\n",
> > + (void*)addr);
> > + return -EAGAIN;
> > + }
> > +
> > + return map_addr;
> > +}
> > +
> > unsigned long __metag_elf_map(struct file *filep, unsigned long addr,
> > struct elf_phdr *eppnt, int prot, int type,
> > unsigned long total_size)
> > @@ -410,11 +433,11 @@ unsigned long __metag_elf_map(struct file *filep, unsigned long addr,
> > */
> > if (total_size) {
> > total_size = ELF_PAGEALIGN(total_size);
> > - map_addr = vm_mmap(filep, addr, total_size, prot, type, off);
> > + map_addr = elf_vm_mmap(filep, addr, total_size, prot, type, off);
> > if (!BAD_ADDR(map_addr))
> > vm_munmap(map_addr+size, total_size-size);
> > } else
> > - map_addr = vm_mmap(filep, addr, size, prot, type, off);
> > + map_addr = elf_vm_mmap(filep, addr, size, prot, type, off);
> >
> > if (!BAD_ADDR(map_addr) && tcm_tag != TCM_INVALID_TAG) {
> > struct tcm_allocation *tcm;
>
> Yeh that looks reasonable to me.

Thanks for double checking. I will make sure to CC you when reposting
the patch after other concerns sort out.

--
Michal Hocko
SUSE Labs

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