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Date: Sat, 6 Mar 2010 14:44:47 -0500 From: Siarhei Liakh <sliakh.lkml@...il.com> To: Ingo Molnar <mingo@...e.hu> Cc: "H. Peter Anvin" <hpa@...or.com>, mingo@...hat.com, jmorris@...ei.org, linux-kernel@...r.kernel.org, arjan@...ux.intel.com, tglx@...utronix.de, jiang@...ncsu.edu, linux-tip-commits@...r.kernel.org Subject: Re: [tip:x86/mm] x86, mm: NX protection for kernel data On Mon, Feb 22, 2010 at 12:21 PM, Ingo Molnar <mingo@...e.hu> wrote: > > * H. Peter Anvin <hpa@...or.com> wrote: > >> On 02/22/2010 03:01 AM, Ingo Molnar wrote: >> >> >> >>> Commit-ID: 01ab31371da90a795b774d87edf2c21bb3a64dda >> >>> Gitweb: http://git.kernel.org/tip/01ab31371da90a795b774d87edf2c21bb3a64dda >> >>> Author: Siarhei Liakh <sliakh.lkml@...il.com> >> >>> AuthorDate: Sun, 31 Jan 2010 18:27:55 -0500 >> >>> Committer: H. Peter Anvin <hpa@...or.com> >> >>> CommitDate: Wed, 17 Feb 2010 10:11:24 -0800 >> >>> >> >>> x86, mm: NX protection for kernel data >> >>> >> >>> This patch expands functionality of CONFIG_DEBUG_RODATA to set main >> >>> (static) kernel data area as NX. >> >> >> >> -tip testing is seeing boot hangs along the lines of: >> >> >> >> [ 15.568108] EXT3-fs (sda1): recovery complete >> >> [ 15.573064] EXT3-fs (sda1): mounted filesystem with ordered data mode >> >> [ 15.580313] VFS: Mounted root (ext3 filesystem) readonly on device 8:1. >> >> [ 15.584021] async_waiting @ 1 >> >> [ 15.588008] async_continuing @ 1 after 0 usec >> >> [ 15.592163] Freeing unused kernel memory: 540k freed >> >> [ 15.600126] NX-protecting the kernel data: c15ab000, 2919 pages >> >> >> >> which i suspect could be due to the commit above. >> > >> > Yep, that's confirmed now, applying these 3 reverts makes it boot fine: >> > >> > 833e0ca: Revert "x86, mm: NX protection for kernel data" >> > ce4b6b4: Revert "x86: RO/NX protection for loadable kernel modules" >> > e357312: Revert "module: fix () used as prototype in include/linux/module.h" >> > >> >> Given that e357312 is a () -> (void) prototype fix, is hardly seems >> likely to be at fault. The RO/NX stuff, on the other hand, make a lot >> of sense. > > Yes, i reverted e357312 because it was a dependent change. I was able to narrow down the issue to spinlock debugging. More specifically, DEBUG_SPINLOCK=y seem to be somehow incompatible with kernel's RW-data being NX. Crash/nocrash config diff: ============================================ diff -uNr config.tip.crash config.tip.nocrash --- config.tip.crash 2010-03-05 22:43:01.000000000 -0500 +++ config.tip.nocrash 2010-03-06 01:38:00.000000000 -0500 @@ -1,7 +1,7 @@ # # Automatically generated make config: don't edit # Linux kernel version: 2.6.33 -# Fri Mar 5 22:22:10 2010 +# Sat Mar 6 01:22:32 2010 # # CONFIG_64BIT is not set CONFIG_X86_32=y @@ -219,27 +219,27 @@ # CONFIG_INLINE_SPIN_LOCK_BH is not set # CONFIG_INLINE_SPIN_LOCK_IRQ is not set # CONFIG_INLINE_SPIN_LOCK_IRQSAVE is not set -# CONFIG_INLINE_SPIN_UNLOCK is not set +CONFIG_INLINE_SPIN_UNLOCK=y # CONFIG_INLINE_SPIN_UNLOCK_BH is not set -# CONFIG_INLINE_SPIN_UNLOCK_IRQ is not set +CONFIG_INLINE_SPIN_UNLOCK_IRQ=y # CONFIG_INLINE_SPIN_UNLOCK_IRQRESTORE is not set # CONFIG_INLINE_READ_TRYLOCK is not set # CONFIG_INLINE_READ_LOCK is not set # CONFIG_INLINE_READ_LOCK_BH is not set # CONFIG_INLINE_READ_LOCK_IRQ is not set # CONFIG_INLINE_READ_LOCK_IRQSAVE is not set -# CONFIG_INLINE_READ_UNLOCK is not set +CONFIG_INLINE_READ_UNLOCK=y # CONFIG_INLINE_READ_UNLOCK_BH is not set -# CONFIG_INLINE_READ_UNLOCK_IRQ is not set +CONFIG_INLINE_READ_UNLOCK_IRQ=y # CONFIG_INLINE_READ_UNLOCK_IRQRESTORE is not set # CONFIG_INLINE_WRITE_TRYLOCK is not set # CONFIG_INLINE_WRITE_LOCK is not set # CONFIG_INLINE_WRITE_LOCK_BH is not set # CONFIG_INLINE_WRITE_LOCK_IRQ is not set # CONFIG_INLINE_WRITE_LOCK_IRQSAVE is not set -# CONFIG_INLINE_WRITE_UNLOCK is not set +CONFIG_INLINE_WRITE_UNLOCK=y # CONFIG_INLINE_WRITE_UNLOCK_BH is not set -# CONFIG_INLINE_WRITE_UNLOCK_IRQ is not set +CONFIG_INLINE_WRITE_UNLOCK_IRQ=y # CONFIG_INLINE_WRITE_UNLOCK_IRQRESTORE is not set # CONFIG_MUTEX_SPIN_ON_OWNER is not set CONFIG_FREEZER=y @@ -331,7 +331,7 @@ CONFIG_FLAT_NODE_MEM_MAP=y CONFIG_SPARSEMEM_STATIC=y CONFIG_PAGEFLAGS_EXTENDED=y -CONFIG_SPLIT_PTLOCK_CPUS=999999 +CONFIG_SPLIT_PTLOCK_CPUS=4 CONFIG_PHYS_ADDR_T_64BIT=y CONFIG_ZONE_DMA_FLAG=1 CONFIG_BOUNCE=y @@ -2808,16 +2808,12 @@ CONFIG_DEBUG_RT_MUTEXES=y CONFIG_DEBUG_PI_LIST=y CONFIG_RT_MUTEX_TESTER=y -CONFIG_DEBUG_SPINLOCK=y +# CONFIG_DEBUG_SPINLOCK is not set CONFIG_DEBUG_MUTEXES=y -CONFIG_DEBUG_LOCK_ALLOC=y -CONFIG_PROVE_LOCKING=y -# CONFIG_PROVE_RCU is not set -CONFIG_LOCKDEP=y +# CONFIG_DEBUG_LOCK_ALLOC is not set +# CONFIG_PROVE_LOCKING is not set # CONFIG_LOCK_STAT is not set -CONFIG_DEBUG_LOCKDEP=y -CONFIG_TRACE_IRQFLAGS=y -CONFIG_DEBUG_SPINLOCK_SLEEP=y +# CONFIG_DEBUG_SPINLOCK_SLEEP is not set CONFIG_DEBUG_LOCKING_API_SELFTESTS=y CONFIG_STACKTRACE=y # CONFIG_DEBUG_KOBJECT is not set ============================================ Kernel crash dump: ============================================ [ 2.844000] EXT3-fs (sda1): warning: maximal mount count reached, running e2fsck is recommended [ 2.848000] EXT3-fs (sda1): using internal journal [ 2.849556] EXT3-fs (sda1): recovery complete [ 2.852000] EXT3-fs (sda1): mounted filesystem with ordered data mode [ 2.854168] VFS: Mounted root (ext3 filesystem) on device 8:1. [ 2.856000] Freeing unused kernel memory (init): 540k freed [ 2.857056] NX-protecting the kernel data: 0xc15b3000 - 0xc1834000, 641 pages [ 2.860328] do_page_fault - entry [ 2.862554] do_page_fault: 0xc17ebdb8 [ 2.864000] do_page_fault - kernel space [ 2.864000] do_page_fault - about to call bad_area_nosemaphore() [ 2.864000] BUG: unable to handle kernel paging request at c17ebdb8 [ 2.864000] IP: [<c12609f7>] do_raw_spin_unlock+0x5e/0x71 [ 2.864000] *pdpt = 00000000018c0001 *pde = 80000000016001e1 [ 2.864000] Oops: 0003 [#1] SMP [ 2.864000] last sysfs file: [ 2.864000] Modules linked in: [ 2.864000] [ 2.864000] Pid: 1, comm: swapper Not tainted 2.6.33-tip+ #41 / [ 2.864000] EIP: 0060:[<c12609f7>] EFLAGS: 00010046 CPU: 0 [ 2.864000] EIP is at do_raw_spin_unlock+0x5e/0x71 [ 2.864000] EAX: 00000000 EBX: c17ebdac ECX: 00000001 EDX: 00000c0b [ 2.864000] ESI: 00000246 EDI: c18c0058 EBP: f780fe14 ESP: f780fe10 [ 2.864000] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 [ 2.864000] Process swapper (pid: 1, ti=f780f000 task=f7826000 task.ti=f780f000) [ 2.864000] Stack: [ 2.864000] c17ebdac f780fe24 c15ad3f2 00000000 00000000 f780ff18 c1017a57 00000000 [ 2.864000] <0> 016001e3 00000000 016001e3 f77a8004 00000001 00000000 00000163 80000000 [ 2.864000] <0> 00000000 ffffffff ffffffff 80000000 000001e1 80000000 00000000 80000000 [ 2.864000] Call Trace: [ 2.864000] [<c15ad3f2>] ? _raw_spin_unlock_irqrestore+0x20/0x3c [ 2.864000] [<c1017a57>] ? __change_page_attr_set_clr+0x65c/0x945 [ 2.864000] [<c1092245>] ? vm_unmap_aliases+0x17b/0x186 [ 2.864000] [<c15b3000>] ? _etext+0x0/0x24 [ 2.864000] [<c1017eb4>] ? change_page_attr_set_clr+0x174/0x312 [ 2.864000] [<c15b3000>] ? _etext+0x0/0x24 [ 2.864000] [<c10182d1>] ? set_memory_nx+0x2d/0x32 [ 2.864000] [<c10163ab>] ? mark_nxdata_nx+0x37/0x41 [ 2.864000] [<c15b3000>] ? _etext+0x0/0x24 [ 2.864000] [<c1834000>] ? i386_start_kernel+0x0/0xaa [ 2.864000] [<c101649d>] ? free_initmem+0x1c/0x1e [ 2.864000] [<c1001148>] ? init_post+0xd/0x121 [ 2.864000] [<c1834401>] ? kernel_init+0x1d5/0x1df [ 2.864000] [<c183422c>] ? kernel_init+0x0/0x1df [ 2.864000] [<c1002e66>] ? kernel_thread_helper+0x6/0x10 [ 2.864000] Code: 54 8b c1 39 43 0c 74 0c ba 74 e1 73 c1 89 d8 e8 31 ff ff ff 64 a1 d8 6b 8b c1 39 43 08 74 0c ba 80 e1 73 c1 89 d8 e8 1a ff ff ff <c7> 43 0c ff ff ff ff c7 43 08 ff ff ff ff fe 03 5b 5d c3 55 89 [ 2.864000] EIP: [<c12609f7>] do_raw_spin_unlock+0x5e/0x71 SS:ESP 0068:f780fe10 [ 2.864000] CR2: 00000000c17ebdb8 [ 2.864000] ---[ end trace 0d94f53e9dfe82f9 ]--- [ 2.948071] swapper used greatest stack depth: 1804 bytes left [ 2.952000] Kernel panic - not syncing: Attempted to kill init! ============================================ looking for c17ebdb8 in system.map points to a location in pgd_lock: ============================================ $grep c17ebd System.map c17ebd68 d bios_check_work c17ebda8 d highmem_pages c17ebdac D pgd_lock c17ebdc8 D pgd_list c17ebdd0 D show_unhandled_signals c17ebdd4 d cpa_lock c17ebdf0 d memtype_lock ============================================ I've looked at the lock debugging and could not find any place that would look like an attempt to execute data. This would lead me to think that calling set_memory_nx from kernel_init somehow confuses the lock debugging subsystem, or set_memory_nx does not change page attributes in a safe manner (for example when a lock is stored inside the page whose attributes are being changed). Any suggestions on how should I proceed forward in troubleshooting this issue? Thank you. View attachment "config.tip.crash" of type "text/x-apport" (70743 bytes) Download attachment "config.tip.nocrash" of type "application/octet-stream" (70622 bytes)
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