On Wed 24-01-18 10:39:41, Anshuman Khandual wrote: > On 01/23/2018 09:36 PM, Michal Hocko wrote: > > On Tue 23-01-18 21:28:28, Anshuman Khandual wrote: > >> On 01/23/2018 06:15 PM, Michal Hocko wrote: > >>> On Tue 23-01-18 16:55:18, Anshuman Khandual wrote: > >>>> On 01/17/2018 01:37 PM, Michal Hocko wrote: > >>>>> On Thu 11-01-18 15:38:37, Anshuman Khandual wrote: > >>>>>> On 01/09/2018 09:43 PM, Michal Hocko wrote: > >>>>> [...] > >>>>>>> Did you manage to catch _who_ is requesting that anonymous mapping? Do > >>>>>>> you need a help with the debugging patch? > >>>>>> > >>>>>> Not yet, will get back on this. > >>>>> > >>>>> ping? > >>>> > >>>> Hey Michal, > >>>> > >>>> Missed this thread, my apologies. This problem is happening only with > >>>> certain binaries like 'sed', 'tmux', 'hostname', 'pkg-config' etc. As > >>>> you had mentioned before the map request collision is happening on > >>>> [10030000, 10040000] and [10030000, 10040000] ranges only which is > >>>> just a single PAGE_SIZE. You asked previously that who might have > >>>> requested the anon mapping which is already present in there ? Would > >>>> not that be the same process itself ? I am bit confused. > >>> > >>> We are early in the ELF loading. If we are mapping over an existing > >>> mapping then we are effectivelly corrupting it. In other words exactly > >>> what this patch tries to prevent. I fail to see what would be a relevant > >>> anon mapping this early and why it would be colliding with elf > >>> segements. > >>> > >>>> Would it be > >>>> helpful to trap all the mmap() requests from any of the binaries > >>>> and see where we might have created that anon mapping ? > >>> > >>> Yeah, that is exactly what I was suggesting. Sorry for not being clear > >>> about that. > >>> > >> > >> Tried to instrument just for the 'sed' binary and dont see any where > >> it actually requests the anon VMA which got hit when loading the ELF > >> section which is strange. All these requested flags here already has > >> MAP_FIXED_NOREPLACE (0x100000). Wondering from where the anon VMA > >> actually came from. > > > > Could you try to dump backtrace? > > This is when it fails inside elf_map() function due to collision with > existing anon VMA mapping. This is not the interesting one. This is the ELF loader. And we know it fails. We are really interested in the one _who_ installs the original VMA. Because nothing should be really there. It would be also very helpful to translate the backtrace with faddr2line to get line numbers. > [c000201c9ad07880] [c000000000b0b4c0] dump_stack+0xb0/0xf0 (unreliable) > [c000201c9ad078c0] [c0000000003c4550] elf_map+0x2d0/0x310 > [c000201c9ad07b60] [c0000000003c6258] load_elf_binary+0x6f8/0x158c > [c000201c9ad07c80] [c000000000352900] search_binary_handler+0xd0/0x270 > [c000201c9ad07d10] [c000000000354838] do_execveat_common.isra.31+0x658/0x890 > [c000201c9ad07df0] [c000000000354e80] SyS_execve+0x40/0x50 > [c000201c9ad07e30] [c00000000000b220] system_call+0x58/0x6c -- Michal Hocko SUSE Labs
