WOLK v4.16s: Grsecurity compile error/bug?

Hi Marc,

I ran into the following compile error in linux-2.4.20-wolk4.16s, with
Grsecurity/Pax options enabled. Specifically, CONFIG_PAX_PAGEEXEC=y


gcc -D__KERNEL__
-I/home/chagmuel/devel/RPM/BUILD/wolk-4.16/linux-2.4.20/include -Wall
-Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -g
-Wno-unused  -Os -fomit-frame-pointer -pipe -mpreferred-stack-boundary=2
-march=i686    -nostdinc -iwithprefix include -DKBUILD_BASENAME=binfmt_elf
-c -o binfmt_elf.o binfmt_elf.c
binfmt_elf.c: In function `load_elf_binary':
binfmt_elf.c:1006: warning: passing arg 2 of `__do_mmap_pgoff' makes pointer
from integer without a cast
binfmt_elf.c:1006: too few arguments to function `__do_mmap_pgoff'
make[2]: *** [binfmt_elf.o] Error 1
make[2]: Leaving directory
`/home/chagmuel/devel/RPM/BUILD/wolk-4.16/linux-2.4.20/fs'


Looking at the offending code in fs/binfmt_elf.c there seems to be an
inconsistancy in the call to __do_mmap_pgoff. Every other call to this
function includes current->mm as the first argument except the call which
caused the error:


#ifdef CONFIG_GRKERNSEC_PAX_PAGEEXEC
    if (current->flags & PF_PAX_PAGEEXEC)
        load_addr_random = __do_mmap_pgoff(NULL,
ELF_PAGESTART(load_bias_random + vaddr), 0UL, elf_prot, elf_flags |
MAP_MIRROR, error);
#endif

#ifdef CONFIG_GRKERNSEC_PAX_SEGMEXEC
    if (current->flags & PF_PAX_SEGMEXEC) {
        if (elf_prot & PROT_EXEC) {
            load_addr_random = __do_mmap_pgoff(current->mm, NULL,
ELF_PAGESTART(load_bias_random + vaddr), elf_ppnt->p_memsz +
ELF_PAGEOFFSET(elf_ppnt->p_vaddr), PROT_NONE, MAP_PRIVATE | MAP_FIXED, 0UL);
            if (!BAD_ADDR(load_addr_random)) {
                load_addr_random = __do_mmap_pgoff(current->mm, NULL,
ELF_PAGESTART(load_bias_random + vaddr + SEGMEXEC_TASK_SIZE), 0UL,
lf_prot, elf_flags | MAP_MIRROR, error);
                if (!BAD_ADDR(load_addr_random))
                    load_addr_random -= SEGMEXEC_TASK_SIZE;
            }
        } else
                load_addr_random = __do_mmap_pgoff(current->mm, NULL,
ELF_PAGESTART(load_bias_random + vaddr), 0UL, elf_prot, elf_flags |
MAP_MIRROR, error);
    }
#endif


The prototype for __do_mmap_pgoff in include/linux/mm.h is as follows:


extern unsigned long __do_mmap_pgoff(struct mm_struct *mm, struct file
*file, unsigned long addr,
	unsigned long len, unsigned long prot,
	unsigned long flag, unsigned long pgoff);


This leads me to believe that the proper call should be as follows:


#ifdef CONFIG_GRKERNSEC_PAX_PAGEEXEC
    if (current->flags & PF_PAX_PAGEEXEC)
        load_addr_random = __do_mmap_pgoff(current->mm, NULL,
ELF_PAGESTART(load_bias_random + vaddr), 0UL, elf_prot, elf_flags |
MAP_MIRROR, error);
                                           ^^^^^^^^^^^
#endif


I realize this is probably a Grsecurity issue, but I wanted to run it by you
first, since I'm very fuzzy on the mmap/rmap issues, and I'm not really a
kernel hacker!  I'm also new to Grsecurity and Pax.  In retrospect, I
probably don't need this option (that's why the issue has never come up
before?) but I need to learn more about the various options.  This was a
first cut following the Grsecurity 'QuickStart Guide'

Let me know what you think.

-- Carl


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