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From: Roman Gushchin To: Parav Pandit Cc: Jason Gunthorpe , Leon Romanovsky , Maher Sanalla , "linux-rdma@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] RDMA/core: fix a NULL-pointer dereference in hw_stat_device_show() Message-ID: References: <20250221020555.4090014-1-roman.gushchin@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT On Fri, Feb 21, 2025 at 08:03:33AM +0000, Parav Pandit wrote: > > From: Roman Gushchin > > Sent: Friday, February 21, 2025 10:20 AM > > > > On Fri, Feb 21, 2025 at 04:34:25AM +0000, Parav Pandit wrote: > > > > > > > From: Roman Gushchin > > > > Sent: Friday, February 21, 2025 9:56 AM > > > > > > > > On Fri, Feb 21, 2025 at 03:14:16AM +0000, Parav Pandit wrote: > > > > > > > > > > > From: Roman Gushchin > > > > > > Sent: Friday, February 21, 2025 7:36 AM > > > > > > > > > > > > Commit 54747231150f ("RDMA: Introduce and use > > > > > > rdma_device_to_ibdev()") introduced rdma_device_to_ibdev() > > > > > > helper which has to be used to obtain an ib_device pointer from a > > device pointer. > > > > > > > > > > > > > > > > > hw_stat_device_show() and hw_stat_device_store() were missed. > > > > > > > > > > > > It causes a NULL pointer dereference panic on an attempt to read > > > > > > hw counters from a namespace, when the device structure is not > > > > > > embedded into the ib_device structure. > > > > > Do you mean net namespace other than default init_net? > > > > > Assuming the answer is yes, some question below. > > > > > > > > > > > In this case casting the device pointer into the ib_device > > > > > > pointer using container_of() is wrong. > > > > > > Instead, rdma_device_to_ibdev() should be used, which uses the > > > > > > back- reference (container_of(device, struct ib_core_device, dev))- > > >owner. > > > > > > > > > > > > [42021.807566] BUG: kernel NULL pointer dereference, address: > > > > > > 0000000000000028 [42021.814463] #PF: supervisor read access in > > > > > > kernel mode [42021.819549] #PF: error_code(0x0000) - not-present > > > > > > page [42021.824636] PGD 0 P4D 0 [42021.827145] Oops: 0000 [#1] > > > > > > SMP PTI [42021.830598] CPU: 82 PID: 2843922 Comm: switchto- > > defaul Kdump: > > > > loaded > > > > > > Tainted: G S W I XXX > > > > > > [42021.841697] Hardware name: XXX [42021.849619] RIP: > > > > > > 0010:hw_stat_device_show+0x1e/0x40 [ib_core] [42021.855362] > > > > > > Code: 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f > > > > > > 44 00 00 49 89 d0 4c 8b 5e 20 48 8b 8f b8 04 00 00 48 81 c7 f0 > > > > > > fa ff ff <48> 8b > > > > > > 41 28 48 29 ce 48 83 c6 d0 48 c1 ee 04 69 d6 ab aa aa aa 48 > > > > > > [42021.873931] > > > > > > RSP: 0018:ffff97fe90f03da0 EFLAGS: 00010287 [42021.879108] RAX: > > > > > > ffff9406988a8c60 RBX: ffff940e1072d438 RCX: 0000000000000000 > > > > > > [42021.886169] RDX: ffff94085f1aa000 RSI: ffff93c6cbbdbcb0 RDI: > > > > > > ffff940c7517aef0 [42021.893230] RBP: ffff97fe90f03e70 R08: > > > > > > ffff94085f1aa000 R09: 0000000000000000 [42021.900294] R10: > > > > > > ffff94085f1aa000 R11: ffffffffc0775680 R12: ffffffff87ca2530 > > > > > > [42021.907355] > > > > > > R13: ffff940651602840 R14: ffff93c6cbbdbcb0 R15: > > > > > > ffff94085f1aa000 [42021.914418] FS: 00007fda1a3b9700(0000) > > > > GS:ffff94453fb80000(0000) > > > > > > knlGS:0000000000000000 [42021.922423] CS: 0010 DS: 0000 ES: > > > > > > 0000 > > > > CR0: > > > > > > 0000000080050033 [42021.928130] CR2: 0000000000000028 CR3: > > > > > > 00000042dcfb8003 CR4: 00000000003726f0 [42021.935194] DR0: > > > > > > 0000000000000000 DR1: 0000000000000000 DR2: > > 0000000000000000 > > > > > > [42021.942257] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: > > > > > > 0000000000000400 [42021.949324] Call Trace: > > > > > > [42021.951756] > > > > > > [42021.953842] [] ? show_regs+0x64/0x70 > > > > > > [42021.959030] [] ? __die+0x78/0xc0 > > > > > > [42021.963874] > > > > [] ? > > > > > > page_fault_oops+0x2b5/0x3b0 [42021.969749] [] ? > > > > > > exc_page_fault+0x1a2/0x3c0 [42021.975549] [] ? > > > > > > asm_exc_page_fault+0x26/0x30 [42021.981517] [] > > ? > > > > > > __pfx_show_hw_stats+0x10/0x10 [ib_core] [42021.988482] > > > > > > [] ? hw_stat_device_show+0x1e/0x40 [ib_core] > > > > > > [42021.995438] [] dev_attr_show+0x1e/0x50 > > > > > > [42022.000803] [] sysfs_kf_seq_show+0x81/0xe0 > > > > > > [42022.006508] [] seq_read_iter+0xf4/0x410 > > > > > > [42022.011954] [] vfs_read+0x16e/0x2f0 > > > > > > [42022.017058] [] ksys_read+0x6e/0xe0 > > > > > > [42022.022073] [] > > > > > > do_syscall_64+0x6a/0xa0 [42022.027441] [] > > > > > > entry_SYSCALL_64_after_hwframe+0x78/0xe2 > > > > > > > > > > > > Fixes: 54747231150f ("RDMA: Introduce and use > > > > > > rdma_device_to_ibdev()") > > > > > Commit eb15c78b05bd9 eliminated hw_counters sysfs directory into > > > > > the > > > > net namespace. > > > > > I don't see it created in any other net ns other than init_net > > > > > with kernel > > > > 6.12+. > > > > > > > > > > I am puzzled. Can you please explain/share the reproduction steps > > > > > for > > > > generating above call trace? > > > > > > > > Hi Parav! > > > > > > > > This bug was spotted in the production on a small number of > > > > machines. They were running a 6.6-based kernel (with no changes > > > > around this code). I don't have a reproducer (and there is no simple > > > > way for me to reproduce the problem), but I've several core dumps > > > > and from inspecting them it was clear that a ib_device pointer > > > > obtained in hw_stat_device_show() was wrong. At the same time the > > > > ib_pointer obtained in the way rdma_device_to_ibdev() works was > > correct. > > > > > > > I just tried reproducing now on 6.12+ kernel manually. > > > > Can you, please, share your steps? Or try the 6.6 kernel? > > > $ rdma system show to display 'netns shared'. > $ ip netns add foo > $ ip netns exec foo bash > $ attempt to access the hw counters from the foo net namespace. Ok, it worked well. The following commands $ ip netns add foo $ ip netns exec foo bash $ cat /sys/class/infiniband/mlx4_0/hw_counters/* cause a panic on a vanilla v6.12.9 without my changes and work perfectly fine with my patch. Thanks!