1. 10 Nov, 2017 1 commit
    • Håkon Bugge's avatar
      rds: ib: Fix NULL pointer dereference in debug code · 1cb483a5
      Håkon Bugge authored
      rds_ib_recv_refill() is a function that refills an IB receive
      queue. It can be called from both the CQE handler (tasklet) and a
      worker thread.
      Just after the call to ib_post_recv(), a debug message is printed with
                  ret = ib_post_recv(ic->i_cm_id->qp, &recv->r_wr, &failed_wr);
                  rdsdebug("recv %p ibinc %p page %p addr %lu ret %d\n", recv,
                           recv->r_ibinc, sg_page(&recv->r_frag->f_sg),
                           (long) ib_sg_dma_address(
      Now consider an invocation of rds_ib_recv_refill() from the worker
      thread, which is preemptible. Further, assume that the worker thread
      is preempted between the ib_post_recv() and rdsdebug() statements.
      Then, if the preemption is due to a receive CQE event, the
      rds_ib_recv_cqe_handler() will be invoked. This function processes
      receive completions, including freeing up data structures, such as the
      In this scenario, rds_ib_recv_cqe_handler() will process the receive
      WR posted above. That implies, that the recv->r_frag has been freed
      before the above rdsdebug() statement has been executed. When it is
      later executed, we will have a NULL pointer dereference:
      [ 4088.068008] BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
      [ 4088.076754] IP: rds_ib_recv_refill+0x87/0x620 [rds_rdma]
      [ 4088.082686] PGD 0 P4D 0
      [ 4088.085515] Oops: 0000 [#1] SMP
      [ 4088.089015] Modules linked in: rds_rdma(OE) rds(OE) rpcsec_gss_krb5(E) nfsv4(E) dns_resolver(E) nfs(E) fscache(E) mlx4_ib(E) ib_ipoib(E) rdma_ucm(E) ib_ucm(E) ib_uverbs(E) ib_umad(E) rdma_cm(E) ib_cm(E) iw_cm(E) ib_core(E) binfmt_misc(E) sb_edac(E) intel_powerclamp(E) coretemp(E) kvm_intel(E) kvm(E) irqbypass(E) crct10dif_pclmul(E) crc32_pclmul(E) ghash_clmulni_intel(E) pcbc(E) aesni_intel(E) crypto_simd(E) iTCO_wdt(E) glue_helper(E) iTCO_vendor_support(E) sg(E) cryptd(E) pcspkr(E) ipmi_si(E) ipmi_devintf(E) ipmi_msghandler(E) shpchp(E) ioatdma(E) i2c_i801(E) wmi(E) lpc_ich(E) mei_me(E) mei(E) mfd_core(E) nfsd(E) auth_rpcgss(E) nfs_acl(E) lockd(E) grace(E) sunrpc(E) ip_tables(E) ext4(E) mbcache(E) jbd2(E) fscrypto(E) mgag200(E) i2c_algo_bit(E) drm_kms_helper(E) syscopyarea(E) sysfillrect(E) sysimgblt(E)
      [ 4088.168486]  fb_sys_fops(E) ahci(E) ixgbe(E) libahci(E) ttm(E) mdio(E) ptp(E) pps_core(E) drm(E) sd_mod(E) libata(E) crc32c_intel(E) mlx4_core(E) i2c_core(E) dca(E) megaraid_sas(E) dm_mirror(E) dm_region_hash(E) dm_log(E) dm_mod(E) [last unloaded: rds]
      [ 4088.193442] CPU: 20 PID: 1244 Comm: kworker/20:2 Tainted: G           OE   4.14.0-rc7.master.20171105.ol7.x86_64 #1
      [ 4088.205097] Hardware name: Oracle Corporation ORACLE SERVER X5-2L/ASM,MOBO TRAY,2U, BIOS 31110000 03/03/2017
      [ 4088.216074] Workqueue: ib_cm cm_work_handler [ib_cm]
      [ 4088.221614] task: ffff885fa11d0000 task.stack: ffffc9000e598000
      [ 4088.228224] RIP: 0010:rds_ib_recv_refill+0x87/0x620 [rds_rdma]
      [ 4088.234736] RSP: 0018:ffffc9000e59bb68 EFLAGS: 00010286
      [ 4088.240568] RAX: 0000000000000000 RBX: ffffc9002115d050 RCX: ffffc9002115d050
      [ 4088.248535] RDX: ffffffffa0521380 RSI: ffffffffa0522158 RDI: ffffffffa0525580
      [ 4088.256498] RBP: ffffc9000e59bbf8 R08: 0000000000000005 R09: 0000000000000000
      [ 4088.264465] R10: 0000000000000339 R11: 0000000000000001 R12: 0000000000000000
      [ 4088.272433] R13: ffff885f8c9d8000 R14: ffffffff81a0a060 R15: ffff884676268000
      [ 4088.280397] FS:  0000000000000000(0000) GS:ffff885fbec80000(0000) knlGS:0000000000000000
      [ 4088.289434] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
      [ 4088.295846] CR2: 0000000000000020 CR3: 0000000001e09005 CR4: 00000000001606e0
      [ 4088.303816] Call Trace:
      [ 4088.306557]  rds_ib_cm_connect_complete+0xe0/0x220 [rds_rdma]
      [ 4088.312982]  ? __dynamic_pr_debug+0x8c/0xb0
      [ 4088.317664]  ? __queue_work+0x142/0x3c0
      [ 4088.321944]  rds_rdma_cm_event_handler+0x19e/0x250 [rds_rdma]
      [ 4088.328370]  cma_ib_handler+0xcd/0x280 [rdma_cm]
      [ 4088.333522]  cm_process_work+0x25/0x120 [ib_cm]
      [ 4088.338580]  cm_work_handler+0xd6b/0x17aa [ib_cm]
      [ 4088.343832]  process_one_work+0x149/0x360
      [ 4088.348307]  worker_thread+0x4d/0x3e0
      [ 4088.352397]  kthread+0x109/0x140
      [ 4088.355996]  ? rescuer_thread+0x380/0x380
      [ 4088.360467]  ? kthread_park+0x60/0x60
      [ 4088.364563]  ret_from_fork+0x25/0x30
      [ 4088.368548] Code: 48 89 45 90 48 89 45 98 eb 4d 0f 1f 44 00 00 48 8b 43 08 48 89 d9 48 c7 c2 80 13 52 a0 48 c7 c6 58 21 52 a0 48 c7 c7 80 55 52 a0 <4c> 8b 48 20 44 89 64 24 08 48 8b 40 30 49 83 e1 fc 48 89 04 24
      [ 4088.389612] RIP: rds_ib_recv_refill+0x87/0x620 [rds_rdma] RSP: ffffc9000e59bb68
      [ 4088.397772] CR2: 0000000000000020
      [ 4088.401505] ---[ end trace fe922e6ccf004431 ]---
      This bug was provoked by compiling rds out-of-tree with
      EXTRA_CFLAGS="-DRDS_DEBUG -DDEBUG" and inserting an artificial delay
      between the rdsdebug() and ib_ib_port_recv() statements:
         	       /* XXX when can this fail? */
      	       ret = ib_post_recv(ic->i_cm_id->qp, &recv->r_wr, &failed_wr);
      +		if (can_wait)
      +			usleep_range(1000, 5000);
      	       rdsdebug("recv %p ibinc %p page %p addr %lu ret %d\n", recv,
      			recv->r_ibinc, sg_page(&recv->r_frag->f_sg),
      			(long) ib_sg_dma_address(
      The fix is simply to move the rdsdebug() statement up before the
      ib_post_recv() and remove the printing of ret, which is taken care of
      anyway by the non-debug code.
      Signed-off-by: default avatarHåkon Bugge <haakon.bugge@oracle.com>
      Reviewed-by: default avatarKnut Omang <knut.omang@oracle.com>
      Reviewed-by: default avatarWei Lin Guay <wei.lin.guay@oracle.com>
      Acked-by: default avatarSantosh Shilimkar <santosh.shilimkar@oracle.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
  2. 09 Aug, 2017 1 commit
  3. 02 Jan, 2017 3 commits
  4. 01 Jul, 2016 1 commit
  5. 15 Jun, 2016 1 commit
  6. 07 Apr, 2016 1 commit
  7. 07 Nov, 2015 1 commit
    • Mel Gorman's avatar
      mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep... · d0164adc
      Mel Gorman authored
      mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd
      __GFP_WAIT has been used to identify atomic context in callers that hold
      spinlocks or are in interrupts.  They are expected to be high priority and
      have access one of two watermarks lower than "min" which can be referred
      to as the "atomic reserve".  __GFP_HIGH users get access to the first
      lower watermark and can be called the "high priority reserve".
      Over time, callers had a requirement to not block when fallback options
      were available.  Some have abused __GFP_WAIT leading to a situation where
      an optimisitic allocation with a fallback option can access atomic
      This patch uses __GFP_ATOMIC to identify callers that are truely atomic,
      cannot sleep and have no alternative.  High priority users continue to use
      __GFP_HIGH.  __GFP_DIRECT_RECLAIM identifies callers that can sleep and
      are willing to enter direct reclaim.  __GFP_KSWAPD_RECLAIM to identify
      callers that want to wake kswapd for background reclaim.  __GFP_WAIT is
      redefined as a caller that is willing to enter direct reclaim and wake
      kswapd for background reclaim.
      This patch then converts a number of sites
      o __GFP_ATOMIC is used by callers that are high priority and have memory
        pools for those requests. GFP_ATOMIC uses this flag.
      o Callers that have a limited mempool to guarantee forward progress clear
        __GFP_DIRECT_RECLAIM but keep __GFP_KSWAPD_RECLAIM. bio allocations fall
        into this category where kswapd will still be woken but atomic reserves
        are not used as there is a one-entry mempool to guarantee progress.
      o Callers that are checking if they are non-blocking should use the
        helper gfpflags_allow_blocking() where possible. This is because
        checking for __GFP_WAIT as was done historically now can trigger false
        positives. Some exceptions like dm-crypt.c exist where the code intent
        is clearer if __GFP_DIRECT_RECLAIM is used instead of the helper due to
        flag manipulations.
      o Callers that built their own GFP flags instead of starting with GFP_KERNEL
        and friends now also need to specify __GFP_KSWAPD_RECLAIM.
      The first key hazard to watch out for is callers that removed __GFP_WAIT
      and was depending on access to atomic reserves for inconspicuous reasons.
      In some cases it may be appropriate for them to use __GFP_HIGH.
      The second key hazard is callers that assembled their own combination of
      GFP flags instead of starting with something like GFP_KERNEL.  They may
      now wish to specify __GFP_KSWAPD_RECLAIM.  It's almost certainly harmless
      if it's missed in most cases as other activity will wake kswapd.
      Signed-off-by: default avatarMel Gorman <mgorman@techsingularity.net>
      Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
      Acked-by: default avatarMichal Hocko <mhocko@suse.com>
      Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
      Cc: Christoph Lameter <cl@linux.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Vitaly Wool <vitalywool@gmail.com>
      Cc: Rik van Riel <riel@redhat.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  8. 05 Oct, 2015 1 commit
  9. 30 Aug, 2015 1 commit
  10. 25 Aug, 2015 4 commits
  11. 18 May, 2015 1 commit
  12. 24 Nov, 2014 1 commit
  13. 18 Apr, 2014 1 commit
  14. 18 Jan, 2014 1 commit
    • Gerald Schaefer's avatar
      net: rds: fix per-cpu helper usage · c196403b
      Gerald Schaefer authored
      commit ae4b46e9
       "net: rds: use this_cpu_* per-cpu helper" broke per-cpu
      handling for rds. chpfirst is the result of __this_cpu_read(), so it is
      an absolute pointer and not __percpu. Therefore, __this_cpu_write()
      should not operate on chpfirst, but rather on cache->percpu->first, just
      like __this_cpu_read() did before.
      Cc: <stable@vger.kernel.org> # 3.8+
      Signed-off-byd Gerald Schaefer <gerald.schaefer@de.ibm.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
  15. 26 Dec, 2012 1 commit
  16. 19 Nov, 2012 1 commit
  17. 20 Mar, 2012 1 commit
  18. 09 Feb, 2012 1 commit
  19. 09 Sep, 2010 17 commits