• Colin Ian King's avatar
    mm/page_idle.c: fix oops because end_pfn is larger than max_pfn · 97e6fe10
    Colin Ian King authored
    commit 7298e3b0a149c91323b3205d325e942c3b3b9ef6 upstream.
    
    Currently the calcuation of end_pfn can round up the pfn number to more
    than the actual maximum number of pfns, causing an Oops.  Fix this by
    ensuring end_pfn is never more than max_pfn.
    
    This can be easily triggered when on systems where the end_pfn gets
    rounded up to more than max_pfn using the idle-page stress-ng stress test:
    
    sudo stress-ng --idle-page 0
    
      BUG: unable to handle kernel paging request at 00000000000020d8
      #PF error: [normal kernel read fault]
      PGD 0 P4D 0
      Oops: 0000 [#1] SMP PTI
      CPU: 1 PID: 11039 Comm: stress-ng-idle- Not tainted 5.0.0-5-generic #6-Ubuntu
      Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
      RIP: 0010:page_idle_get_page+0xc8/0x1a0
      Code: 0f b1 0a 75 7d 48 8b 03 48 89 c2 48 c1 e8 33 83 e0 07 48 c1 ea 36 48 8d 0c 40 4c 8d 24 88 49 c1 e4 07 4c 03 24 d5 00 89 c3 be <49> 8b 44 24 58 48 8d b8 80 a1 02 00 e8 07 d5 77 00 48 8b 53 08 48
      RSP: 0018:ffffafd7c672fde8 EFLAGS: 00010202
      RAX: 0000000000000005 RBX: ffffe36341fff700 RCX: 000000000000000f
      RDX: 0000000000000284 RSI: 0000000000000275 RDI: 0000000001fff700
      RBP: ffffafd7c672fe00 R08: ffffa0bc34056410 R09: 0000000000000276
      R10: ffffa0bc754e9b40 R11: ffffa0bc330f6400 R12: 0000000000002080
      R13: ffffe36341fff700 R14: 0000000000080000 R15: ffffa0bc330f6400
      FS: 00007f0ec1ea5740(0000) GS:ffffa0bc7db00000(0000) knlGS:0000000000000000
      CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
      CR2: 00000000000020d8 CR3: 0000000077d68000 CR4: 00000000000006e0
      Call Trace:
        page_idle_bitmap_write+0x8c/0x140
        sysfs_kf_bin_write+0x5c/0x70
        kernfs_fop_write+0x12e/0x1b0
        __vfs_write+0x1b/0x40
        vfs_write+0xab/0x1b0
        ksys_write+0x55/0xc0
        __x64_sys_write+0x1a/0x20
        do_syscall_64+0x5a/0x110
        entry_SYSCALL_64_after_hwframe+0x44/0xa9
    
    Link: http://lkml.kernel.org/r/20190618124352.28307-1-colin.king@canonical.com
    Fixes: 33c3fc71 ("mm: introduce idle page tracking")
    Signed-off-by: 's avatarColin Ian King <colin.king@canonical.com>
    Reviewed-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
    Acked-by: 's avatarVladimir Davydov <vdavydov.dev@gmail.com>
    Cc: Michal Hocko <mhocko@suse.com>
    Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
    Cc: Mel Gorman <mgorman@techsingularity.net>
    Cc: Stephen Rothwell <sfr@canb.auug.org.au>
    Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: 's avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    97e6fe10