On 10/17/17 at 02:56pm, Michal Hocko wrote: > On Tue 17-10-17 20:26:14, Baoquan He wrote: > > Hi Michal, > > > > Earlier I posted a patchset to clean up these in a different way, but > > patches sent to your below mail address are all rejected. > > > > <[email protected]>: host mail.kerne.org[104.131.33.237] said: 454 4.1.1 > > <[email protected]>: Recipient address rejected: User unknown in virtual > > mailbox table (in reply to RCPT TO command) > > yes, there was a typo in the email address which I've fixed up in the > reply... Your cleanup was mostly about replacing vm_mmap by > get_unmaped_area which is an independent issue to what I am trying to > achieve here.
Oops. Yes, I must have typed your address by hand, but not copying from the previous discussion thread. Sorry for that. > > > On 10/16/17 at 03:44pm, Michal Hocko wrote: > > > From: Michal Hocko <[email protected]> > > > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > > > index 6466153f2bf0..09456e2add18 100644 > > > --- a/fs/binfmt_elf.c > > > +++ b/fs/binfmt_elf.c > > > @@ -341,6 +341,29 @@ create_elf_tables(struct linux_binprm *bprm, struct > > > elfhdr *exec, > > > > > > #ifndef elf_map > > > > > > +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; > > > +} > > > + > > > static unsigned long elf_map(struct file *filep, unsigned long addr, > > > struct elf_phdr *eppnt, int prot, int type, > > > unsigned long total_size) > > > @@ -366,11 +389,11 @@ static unsigned long 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); > > > > Here we will still take the map total, then unmap the rest way. > > > > I am wondering why we don't fix those issues we figured out, but add > > another level of wrapper elf_vm_mmap() to hack it. > > Could you be more specific please? In the current code, obviously the total size for PIE loading is unnecessary since it's MAP_FIXED, and it's initial mapping from ELF_ET_DYN_BASE, I can't see any chance it will fail to map. Though you use a trick in this new elf_vm_mmap() to check if it failed on mapping, in essence it's a MAP_FIXED. And as I said before, then we will still have the ungraceful 'mapping total'|'unmapping the rest' method. If from a new code reader's point of view, the newly added elf_vm_mmap() plus the existing elf_map() may confuse people more. Just personnal opinion. Anyway, your patches are better, my patches have been resting there for several days but no comment. :-) I may still need strength the understanding about elf loading code. Thanks Baoquan > > > So we will have > > elf_map() -> elf_vm_mmap() -> vm_mmap(), not even counting > > vm_mmap_pgoff(), then finally enter into do_mmap_pgoff(), to do the > > maping for elf program. > > I've added another level of helper to keep the code in elf_map saner. It > is quite complex already. > -- > Michal Hocko > SUSE Labs
