On Thu, Dec 17, 2020 at 10:42:02AM +0300, Cyrill Gorcunov wrote: > On Wed, Dec 16, 2020 at 08:29:30PM -0500, Keno Fischer wrote: > > Hi all, > > > > The code in prctl(PR_SET_MM, ...) performs a number of sanity checks, > > among them > > > > ``` > > /* > > * @brk should be after @end_data in traditional maps. > > */ > > if (prctl_map->start_brk <= prctl_map->end_data || > > prctl_map->brk <= prctl_map->end_data) > > goto out; > > ``` > > > > Thanks for pointing, Keno! I don't remember the details right now, > gimme some time and once I refresh my memory I'll reply with > details.
Indeed, when loaded via ld directly we've got a different layout: # /lib64/ld-linux-x86-64.so.2 ~/t start_code 7fc25b0a4000 end_code 7fc25b0c4524 start_stack 7fffcc6b2400 start_data 7fc25b0ce4c0 end_data 7fc25b0cff98 start_brk 55555710c000 sbrk(0) 55555710c000 Note though that as far as I understand the layout is provided by ld loader. I contrast the regular load # ~/t start_code 401000 end_code 401a15 start_stack 7ffce4577dd0 start_data 403e10 end_data 40408c start_brk b5b000 sbrk(0) b5b000 I fear we've not been using ld's loaded programs in c/r procedure much that's why it has not been noted earlier. Need to think how to fix it. Using the whole memory map for verification procedure is a correct way thus the commit you mention is doing exactly what it should but we need to figure out how to deal with fdpic loaded files... I'll back once I figure it out (hopefully more-less soon). Thanks a huge for report!