Subject: Re: mmotm 2018-01-04-16-19 uploaded

From: Anshuman Khandual <[email-masked]>
Date: Sun, 7 Jan 2018 12:19:32 +0530

On 01/05/2018 02:16 PM, Michal Hocko wrote:
> On Fri 05-01-18 12:13:17, Anshuman Khandual wrote:
>> On 01/05/2018 05:50 AM, [email-masked] wrote:
>>> The mm-of-the-moment snapshot 2018-01-04-16-19 has been uploaded to

[...]

>>>
>>> This tree is partially included in linux-next.  To see which patches are
>>> included in linux-next, consult the `series' file.  Only the patches
>>> within the #NEXT_PATCHES_START/#NEXT_PATCHES_END markers are included in
>>> linux-next.
>>>
>>> A git tree which contains the memory management portion of this tree is
>>> maintained at git://git.kernel.org/pub/scm/linux/kernel/git/mhocko/mm.git
>> Seems like this latest snapshot mmotm-2018-01-04-16-19 has not been
>> updated in this git tree. I could not fetch not it shows up in the
>> http link below.
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/mhocko/mm.git
> I will update the tree today (WIP). This is not a fully automated
> process and Andrew pushed his tree during my night ;) So be patient
> please. My tree is non-rebasing which means I cannot just throw the old
> tree away and regenerate it from scratch.
> 
>> The last one mmotm-2017-12-22-17-55 seems to have some regression on
>> powerpc with respect to ELF loading of binaries (see below). Seems to
>> be related to recent MAP_FIXED_SAFE (or MAP_FIXED_NOREPLACE as seen
>> now in the code). IIUC (have not been following the series last month)
>> MAP_FIXED_NOREPLACE will fail an allocation request if the hint address
>> cannot be reserve instead of changing existing mappings.
> Correct
> 
>> Is it possible
>> that ELF loading needs to be fixed at a higher level to deal with these
>> new possible mmap() failures because of MAP_FIXED_NOREPLACE ?
> Could you give us more information about the failure please. Debugging
> patch from http://lkml.kernel.org/r/[email-masked]
> should help to see what is the clashing VMA.

Seems like its re-requesting the same mapping again.

[   23.423642] 9148 (sed): Uhuuh, elf segment at 0000000010030000 requested but the memory is mapped already
[   23.423706] requested [10030000, 10040000] mapped [10030000, 10040000] 100073 anon
[   23.426089] 9151 (sed): Uhuuh, elf segment at 0000000010030000 requested but the memory is mapped already
[   23.426232] requested [10030000, 10040000] mapped [10030000, 10040000] 100073 anon
[   23.429048] 9154 (sed): Uhuuh, elf segment at 0000000010030000 requested but the memory is mapped already
[   23.429196] requested [10030000, 10040000] mapped [10030000, 10040000] 100073 anon
[   23.482766] 9164 (sed): Uhuuh, elf segment at 0000000010030000 requested but the memory is mapped already
[   23.482904] requested [10030000, 10040000] mapped [10030000, 10040000] 100073 anon
[   23.485849] 9167 (sed): Uhuuh, elf segment at 0000000010030000 requested but the memory is mapped already
[   23.485945] requested [10030000, 10040000] mapped [10030000, 10040000] 100073 anon
[   76.041836] 9262 (hostname): Uhuuh, elf segment at 0000000010020000 requested but the memory is mapped already
[   76.041965] requested [10020000, 10030000] mapped [10020000, 10030000] 100073 anon
[   76.207197] 9285 (pkg-config): Uhuuh, elf segment at 0000000010020000 requested but the memory is mapped already
[   76.207326] requested [10020000, 10030000] mapped [10020000, 10030000] 100073 anon
[   76.371073] 9299 (sed): Uhuuh, elf segment at 0000000010030000 requested but the memory is mapped already
[   76.371165] requested [10030000, 10040000] mapped [10030000, 10040000] 100073 anon

I have fixed/changed the debug patch a bit

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index d8c5657..a43eccaa 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -372,11 +372,35 @@ static unsigned long elf_map(struct file *filep, unsigned long addr,
        } else
                map_addr = vm_mmap(filep, addr, size, prot, type, off);

-       if ((type & MAP_FIXED_NOREPLACE) && BAD_ADDR(map_addr))
+       if ((type & MAP_FIXED_NOREPLACE) && BAD_ADDR(map_addr)) {
+               struct vm_area_struct *vma;
+               unsigned long end;
+
+               if (total_size)
+                       end = addr + total_size;
+               else
+                       end = addr + size;
+
                pr_info("%d (%s): Uhuuh, elf segment at %p requested but the memory is mapped already\n",
                                task_pid_nr(current), current->comm,
                                (void *)addr);

+               vma = find_vma(current->mm, addr);
+               if (vma && vma->vm_start <= addr) {
+                       pr_info("requested [%lx, %lx] mapped [%lx, %lx] %lx ", addr, end,
+                                       vma->vm_start, vma->vm_end, vma->vm_flags);
+                       if (!vma->vm_file) {
+                               pr_cont("anon\n");
+                       } else {
+                               char path[512];
+                               char *p = file_path(vma->vm_file, path, sizeof(path));
+                               if (IS_ERR(p))
+                                       p = "?";
+                               pr_cont("\"%s\"\n", kbasename(p));
+                       }
+                       dump_stack();
+               }
+       }
        return(map_addr);
 }

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