Hi, I am writing some code where I lock down a process memory at exec() time. My patches were working fine till 3.9-rc4 and suddendly things broke down in 3.9-rc5.
Whenever I tried to exec() a process with memory locked down, my bash session hangs and after a while I get following warning. login: [ 174.669002] INFO: rcu_sched self-detected stall on CPU { 2} (t=60000 jiffies g=2580 c=2579 q=1085) [ 174.669002] Pid: 4894, comm: kexec Not tainted 3.9.0-rc6+ #243 [ 174.669002] Call Trace: [ 174.669002] <IRQ> [<ffffffff810c413a>] rcu_check_callbacks+0x21a/0x760 [ 174.669002] [<ffffffff810c7c0c>] ? acct_account_cputime+0x1c/0x20 [ 174.669002] [<ffffffff8104fd08>] update_process_times+0x48/0x80 [ 174.669002] [<ffffffff810913dd>] tick_sched_handle+0x3d/0x50 [ 174.669002] [<ffffffff810915e5>] tick_sched_timer+0x45/0x70 [ 174.669002] [<ffffffff81066951>] __run_hrtimer+0x81/0x220 [ 174.669002] [<ffffffff810915a0>] ? tick_nohz_handler+0xa0/0xa0 [ 174.669002] [<ffffffff8108ae0c>] ? ktime_get_update_offsets+0x4c/0xd0 [ 174.669002] [<ffffffff81067297>] hrtimer_interrupt+0xf7/0x250 [ 174.669002] [<ffffffff81886739>] smp_apic_timer_interrupt+0x69/0x99 [ 174.669002] [<ffffffff818859ca>] apic_timer_interrupt+0x6a/0x70 [ 174.669002] <EOI> [<ffffffff8111e557>] ? __mlock_vma_pages_range+0x57/0x70 [ 174.669002] [<ffffffff8111e568>] ? __mlock_vma_pages_range+0x68/0x70 [ 174.669002] [<ffffffff8111ea01>] __mm_populate+0x71/0x140 [ 174.669002] [<ffffffff81121b5f>] vm_brk+0x7f/0xa0 [ 174.669002] [<ffffffff81199633>] load_elf_binary+0x1a73/0x1b10 [ 174.669002] [<ffffffff812d25a5>] ? ima_bprm_check+0x55/0x70 [ 174.669002] [<ffffffff8114890a>] search_binary_handler+0x12a/0x3b0 [ 174.669002] [<ffffffff81197bc0>] ? load_elf_library+0x210/0x210 [ 174.669002] [<ffffffff8114aa00>] do_execve_common+0x500/0x5c0 [ 174.669002] [<ffffffff8114aaf7>] do_execve+0x37/0x40 [ 174.669002] [<ffffffff8114ad9d>] sys_execve+0x3d/0x60 [ 174.669002] [<ffffffff81885379>] stub_execve+0x69/0xa0 I did a git bisect and bisection says that following is first bad commit. commit 09a9f1d27892255cfb9c91203f19476765e2d8d1 Author: Michel Lespinasse <wal...@google.com> Date: Thu Mar 28 16:26:23 2013 -0700 Revert "mm: introduce VM_POPULATE flag to better deal with racy userspace pr This reverts commit 186930500985 ("mm: introduce VM_POPULATE flag to better deal with racy userspace programs"). I reverted above commit and problem gets fixed. Following is my simple patch to lock down a selected process memory. Index: linux-2.6/fs/binfmt_elf.c =================================================================== --- linux-2.6.orig/fs/binfmt_elf.c 2013-04-13 01:50:26.380184101 -0400 +++ linux-2.6/fs/binfmt_elf.c 2013-04-13 01:50:49.827184821 -0400 @@ -721,6 +721,10 @@ static int load_elf_binary(struct linux_ /* OK, This is the point of no return */ current->mm->def_flags = def_flags; + if (!strcmp(bprm->filename, "/sbin/kexec")) { + printk("Memlocking /sbin/kexec\n"); + current->mm->def_flags |= VM_LOCKED; + } /* Do this immediately, since STACK_TOP as used in setup_arg_pages may depend on the personality. */ Do you have any thoughts on what's going on. I am wondering if it indicates a bigger problem which can then be triggered from other paths too. Thanks Vivek -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/