Hello, On Fri, Oct 18, 2013 at 04:15:17PM +0800, linx.z.chen@xxxxxxxxx wrote: > From: Chen LinX <linx.z.chen@xxxxxxxxx> > > When walk_page_range walk a memory map's page tables, it'll skip VM_PFNMAP area, > then variable 'next' will to assign to vma->vm_end, it maybe larger than 'end'. > In next loop, 'addr' will be larger than 'next'. Then in /proc/XXXX/pagemap file > reading procedure, the 'addr' will growing forever in pagemap_pte_range, > pte_to_pagemap_entry will access wrong pte. > > [ 93.387934] BUG: Bad page map in process procrank pte:8437526f pmd:785de067 > [ 93.387936] addr:9108d000 vm_flags:00200073 anon_vma:f0d99020 mapping: (null) index:9108d > [ 93.387938] CPU: 1 PID: 4974 Comm: procrank Tainted: G B W O 3.10.1+ #1 > [ 93.387942] f0d983c8 f0d983c8 e8271e48 c281ef4b e8271e84 c20ee794 c2a3f150 9108d000 > [ 93.387946] 00200073 f0d99020 00000000 0009108d e8342d90 8437526f 0009108d 00000000 > [ 93.387950] 00000000 00084375 fffa4234 e8271e98 c20ef836 00000000 e8271f28 f0d983c8 > [ 93.387951] Call Trace: > [ 93.387953] [<c281ef4b>] dump_stack+0x16/0x18 > [ 93.387956] [<c20ee794>] print_bad_pte+0x114/0x1b0 > [ 93.387959] [<c20ef836>] vm_normal_page+0x56/0x60 > [ 93.387961] [<c21594ba>] pagemap_pte_range+0x17a/0x1d0 > [ 93.387963] [<c2159340>] ? m_next+0x70/0x70 > [ 93.387966] [<c20fc60e>] walk_page_range+0x19e/0x2c0 > [ 93.387969] [<c20432c4>] ? ptrace_may_access+0x24/0x40 > [ 93.387971] [<c2159a4e>] pagemap_read+0x16e/0x200 > [ 93.387973] [<c2159340>] ? m_next+0x70/0x70 > [ 93.387976] [<c2158be0>] ? quota_send_warning+0x1f0/0x1f0 > [ 93.387979] [<c2158c30>] ? pagemap_pte_hole+0x50/0x50 > [ 93.387981] [<c21598e0>] ? clear_refs_pte_range+0xc0/0xc0 > [ 93.387984] [<c210c534>] vfs_read+0x84/0x150 > [ 93.387986] [<c21598e0>] ? clear_refs_pte_range+0xc0/0xc0 > [ 93.387988] [<c210c77a>] SyS_read+0x4a/0x80 > [ 93.387991] [<c28267c8>] syscall_call+0x7/0xb > [ 93.387996] [<c2820000>] ? e1000_regdump+0x6f/0x37c > [ 102.866190] [<c259fcd3>] ? cpuidle_idle_call+0x93/0x1b0 > [ 102.872124] [<c28297fa>] ? atomic_notifier_call_chain+0x1a/0x20 > [ 102.878834] [<c2008478>] ? arch_cpu_idle+0x8/0x20 > [ 102.884183] [<c207950d>] ? cpu_startup_entry+0x4d/0x1b0 > [ 102.890116] [<c280ecbd>] ? rest_init+0x5d/0x60 > [ 102.895174] [<c2b989f8>] ? start_kernel+0x31b/0x321 > [ 102.900717] [<c2b98512>] ? repair_env_string+0x51/0x51 > [ 102.906551] [<c2b98356>] ? i386_start_kernel+0x12c/0x12f > > Signed-off-by: Liu ShuoX <shuox.liu@xxxxxxxxx> > Signed-off-by: Chen LinX <linx.z.chen@xxxxxxxxx> > --- > mm/pagewalk.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/pagewalk.c b/mm/pagewalk.c > index 5da2cbc..2beeabf 100644 > --- a/mm/pagewalk.c > +++ b/mm/pagewalk.c > @@ -242,7 +242,7 @@ int walk_page_range(unsigned long addr, unsigned long end, > if (err) > break; > pgd++; > - } while (addr = next, addr != end); > + } while (addr = next, addr < end); > > return err; > } I agree to this change. Reviewed-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> BTW, walk_(pte|pmd|pud|hugetlb)_range also have the same condition (addr != end), so I think that it's safer to change them too. And I think that it's worth sending to -stable. The VM_PFNMAP check is introduced around v3.10-rc2, so 3.10.X and 3.11.X should want this fix. Thanks, Naoya Horiguchi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>