Fixes: 35d4a0b63dc0c6d1177d4f532a9deae958f0662c ("IB/uverbs: Fix race between ib_uverbs_open and remove_one") While testing ocrdma for disassociate_ucontext support following kernel panic was seen: BUG: unable to handle kernel paging request at ffffffffa07ccd7a [67139.981020] IP: [<ffffffffa07ccd7a>] 0xffffffffa07ccd7a [67139.987185] PGD 19c5067 PUD 19c6063 PMD 469d08067 PTE 0 [67139.993370] Oops: 0010 [#1] SMP [67140.257286] Call Trace: [67140.260665] [<ffffffff810c16a0>] ? prepare_to_wait_event+0xf0/0xf0 [67140.268337] [<ffffffffa04cabc3>] ? ib_dereg_mr+0x23/0x30 [ib_core] [67140.276009] [<ffffffffa03ee5f0>] ? ib_uverbs_cleanup_ucontext+0x320/0x440 [ib_uverbs] [67140.285550] [<ffffffffa03ee9e9>] ? ib_uverbs_close+0x59/0xb0 [ib_uverbs] [67140.293807] [<ffffffff811ff744>] ? __fput+0xe4/0x210 [67140.300132] [<ffffffff811ff8ae>] ? ____fput+0xe/0x10 [67140.306457] [<ffffffff8109b697>] ? task_work_run+0x77/0x90 [67140.313388] [<ffffffff81081af2>] ? do_exit+0x2d2/0xab0 [67140.319910] [<ffffffff8108234f>] ? do_group_exit+0x3f/0xa0 [67140.326821] [<ffffffff8108d54c>] ? get_signal+0x1cc/0x5e0 [67140.333635] [<ffffffff81017387>] ? do_signal+0x37/0x660 [67140.340257] [<ffffffffa021669a>] ? ucma_write+0x7a/0xc0 [rdma_ucm] [67140.347949] [<ffffffff81079c37>] ? exit_to_usermode_loop+0x59/0xa2 [67140.355651] [<ffffffff81003bad>] ? syscall_return_slowpath+0x8d/0xa0 [67140.363554] [<ffffffff81680dcc>] ? int_ret_from_sys_call+0x25/0x8f [67140.371259] Code: Bad RIP value. [67140.375678] RIP [<ffffffffa07ccd7a>] 0xffffffffa07ccd7a [67140.382314] RSP <ffff880867727ad8> [67140.386894] CR2: ffffffffa07ccd7a [67140.393737] ---[ end trace 807b4472c30412d0 ]--- [67141.682413] Kernel panic - not syncing: Fatal exception [67141.682431] Kernel Offset: disabled [67141.733934] ---[ end Kernel panic - not syncing: Fatal exception Root Cause: During rmmod <vendor-driver> "ib_uverbs_close()" context is still running, while "ib_uverbs_remove_one()" context completes and ends up freeing ib_dev pointer, thus causing a Kernel Panic. This patch fixes the race. ib_uverbs_close validates dev->ib_dev against NULL inside an srcu lock. If it is NULL, it waits for a completion and drops the srcu else continues with the normal flow. CC: Yishai Hadas <yishaih@xxxxxxxxxxxx> Signed-off-by: Devesh Sharma <devesh.sharma@xxxxxxxxxxxx> --- drivers/infiniband/core/uverbs.h | 1 + drivers/infiniband/core/uverbs_main.c | 19 +++++++++++++++++-- 2 files changed, 18 insertions(+), 2 deletions(-) diff --git a/drivers/infiniband/core/uverbs.h b/drivers/infiniband/core/uverbs.h index 612ccfd..94a7339 100644 --- a/drivers/infiniband/core/uverbs.h +++ b/drivers/infiniband/core/uverbs.h @@ -121,6 +121,7 @@ struct ib_uverbs_file { struct ib_event_handler event_handler; struct ib_uverbs_event_file *async_file; struct list_head list; + struct completion fcomp; int is_closed; }; diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c index 39680ae..f1948bc 100644 --- a/drivers/infiniband/core/uverbs_main.c +++ b/drivers/infiniband/core/uverbs_main.c @@ -928,6 +928,7 @@ static int ib_uverbs_open(struct inode *inode, struct file *filp) file->async_file = NULL; kref_init(&file->ref); mutex_init(&file->mutex); + init_completion(&file->fcomp); filp->private_data = file; kobject_get(&dev->kobj); @@ -954,21 +955,33 @@ static int ib_uverbs_close(struct inode *inode, struct file *filp) struct ib_uverbs_file *file = filp->private_data; struct ib_uverbs_device *dev = file->device; struct ib_ucontext *ucontext = NULL; + struct ib_device *ib_dev; + int srcu_key; + + srcu_key = srcu_read_lock(&dev->disassociate_srcu); + ib_dev = srcu_dereference(dev->ib_dev, + &dev->disassociate_srcu); + if (!ib_dev) + goto out; - mutex_lock(&file->device->lists_mutex); + mutex_lock(&dev->lists_mutex); ucontext = file->ucontext; file->ucontext = NULL; if (!file->is_closed) { list_del(&file->list); file->is_closed = 1; } - mutex_unlock(&file->device->lists_mutex); + mutex_unlock(&dev->lists_mutex); if (ucontext) ib_uverbs_cleanup_ucontext(file, ucontext); if (file->async_file) kref_put(&file->async_file->ref, ib_uverbs_release_event_file); + complete(&file->fcomp); +out: + wait_for_completion(&file->fcomp); + srcu_read_unlock(&dev->disassociate_srcu, srcu_key); kref_put(&file->ref, ib_uverbs_release_file); kobject_put(&dev->kobj); @@ -1199,6 +1212,8 @@ static void ib_uverbs_free_hw_resources(struct ib_uverbs_device *uverbs_dev, } mutex_lock(&uverbs_dev->lists_mutex); + + complete(&file->fcomp); kref_put(&file->ref, ib_uverbs_release_file); } -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html