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    Subject[PATCH V2 2/2] uio: fix crash after the device is unregistered
    Date
    From: Xiubo Li <xiubli@redhat.com>

    For the target_core_user use case, after the device is unregistered
    it maybe still opened in user space, then the kernel will crash, like:

    [ 251.163692] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
    [ 251.163820] IP: [<ffffffffc0736213>] show_name+0x23/0x40 [uio]
    [ 251.163965] PGD 8000000062694067 PUD 62696067 PMD 0
    [ 251.164097] Oops: 0000 [#1] SMP
    ...
    [ 251.165605] e1000 mptscsih mptbase drm_panel_orientation_quirks dm_mirror dm_region_hash dm_log dm_mod
    [ 251.166014] CPU: 0 PID: 13380 Comm: tcmu-runner Kdump: loaded Not tainted 3.10.0-916.el7.test.x86_64 #1
    [ 251.166381] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 05/19/2017
    [ 251.166747] task: ffff971eb91db0c0 ti: ffff971e9e384000 task.ti: ffff971e9e384000
    [ 251.167137] RIP: 0010:[<ffffffffc0736213>] [<ffffffffc0736213>] show_name+0x23/0x40 [uio]
    [ 251.167563] RSP: 0018:ffff971e9e387dc8 EFLAGS: 00010282
    [ 251.167978] RAX: 0000000000000000 RBX: ffff971e9e3f8000 RCX: ffff971eb8368d98
    [ 251.168408] RDX: ffff971e9e3f8000 RSI: ffffffffc0738084 RDI: ffff971e9e3f8000
    [ 251.168856] RBP: ffff971e9e387dd0 R08: ffff971eb8bc0018 R09: 0000000000000000
    [ 251.169296] R10: 0000000000001000 R11: ffffffffa09d444d R12: ffffffffa1076e80
    [ 251.169750] R13: ffff971e9e387f18 R14: 0000000000000001 R15: ffff971e9cfb1c80
    [ 251.170213] FS: 00007ff37d175880(0000) GS:ffff971ebb600000(0000) knlGS:0000000000000000
    [ 251.170693] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    [ 251.171248] CR2: 0000000000000008 CR3: 00000000001f6000 CR4: 00000000003607f0
    [ 251.172071] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    [ 251.172640] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    [ 251.173236] Call Trace:
    [ 251.173789] [<ffffffffa0c9b2d3>] dev_attr_show+0x23/0x60
    [ 251.174356] [<ffffffffa0f561b2>] ? mutex_lock+0x12/0x2f
    [ 251.174892] [<ffffffffa0ac6d9f>] sysfs_kf_seq_show+0xcf/0x1f0
    [ 251.175433] [<ffffffffa0ac54e6>] kernfs_seq_show+0x26/0x30
    [ 251.175981] [<ffffffffa0a63be0>] seq_read+0x110/0x3f0
    [ 251.176609] [<ffffffffa0ac5d45>] kernfs_fop_read+0xf5/0x160
    [ 251.177158] [<ffffffffa0a3d3af>] vfs_read+0x9f/0x170
    [ 251.177707] [<ffffffffa0a3e27f>] SyS_read+0x7f/0xf0
    [ 251.178268] [<ffffffffa0f648af>] system_call_fastpath+0x1c/0x21
    [ 251.178823] Code: 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 53 48 89 d3 e8 7e 96 56 e0 48 8b 80 d8 02 00 00 48 89 df 48 c7 c6 84 80 73 c0 <48> 8b 50 08 31 c0 e8 e2 67 44 e0 5b 48 98 5d c3 0f 1f 00 66 2e
    [ 251.180115] RIP [<ffffffffc0736213>] show_name+0x23/0x40 [uio]
    [ 251.180820] RSP <ffff971e9e387dc8>
    [ 251.181473] CR2: 0000000000000008

    CC: Hamish Martin <hamish.martin@alliedtelesis.co.nz>
    CC: Mike Christie <mchristi@redhat.com>
    Signed-off-by: Xiubo Li <xiubli@redhat.com>
    ---
    drivers/uio/uio.c | 109 ++++++++++++++++++++++++++++++++++++++++++++++--------
    1 file changed, 93 insertions(+), 16 deletions(-)

    diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
    index 33c3bfe..5fe3ca5 100644
    --- a/drivers/uio/uio.c
    +++ b/drivers/uio/uio.c
    @@ -215,7 +215,20 @@ static ssize_t name_show(struct device *dev,
    struct device_attribute *attr, char *buf)
    {
    struct uio_device *idev = dev_get_drvdata(dev);
    - return sprintf(buf, "%s\n", idev->info->name);
    + int ret;
    +
    + mutex_lock(&minor_lock);
    + if (!idev->info) {
    + ret = -EINVAL;
    + dev_err(dev, "the device has been unregistered\n");
    + goto out;
    + }
    +
    + ret = sprintf(buf, "%s\n", idev->info->name);
    +
    +out:
    + mutex_unlock(&minor_lock);
    + return ret;
    }
    static DEVICE_ATTR_RO(name);

    @@ -223,7 +236,20 @@ static ssize_t version_show(struct device *dev,
    struct device_attribute *attr, char *buf)
    {
    struct uio_device *idev = dev_get_drvdata(dev);
    - return sprintf(buf, "%s\n", idev->info->version);
    + int ret;
    +
    + mutex_lock(&minor_lock);
    + if (!idev->info) {
    + ret = -EINVAL;
    + dev_err(dev, "the device has been unregistered\n");
    + goto out;
    + }
    +
    + ret = sprintf(buf, "%s\n", idev->info->version);
    +
    +out:
    + mutex_unlock(&minor_lock);
    + return ret;
    }
    static DEVICE_ATTR_RO(version);

    @@ -399,7 +425,12 @@ static void uio_free_minor(struct uio_device *idev)
    */
    void uio_event_notify(struct uio_info *info)
    {
    - struct uio_device *idev = info->uio_dev;
    + struct uio_device *idev;
    +
    + if (!info)
    + return;
    +
    + idev = info->uio_dev;

    atomic_inc(&idev->event);
    wake_up_interruptible(&idev->wait);
    @@ -415,8 +446,12 @@ void uio_event_notify(struct uio_info *info)
    static irqreturn_t uio_interrupt(int irq, void *dev_id)
    {
    struct uio_device *idev = (struct uio_device *)dev_id;
    - irqreturn_t ret = idev->info->handler(irq, idev->info);
    + irqreturn_t ret;
    +
    + if (!idev->info)
    + return -EINVAL;

    + ret = idev->info->handler(irq, idev->info);
    if (ret == IRQ_HANDLED)
    uio_event_notify(idev->info);

    @@ -460,6 +495,12 @@ static int uio_open(struct inode *inode, struct file *filep)
    filep->private_data = listener;

    mutex_lock(&idev->info_lock);
    + if (!idev->info) {
    + mutex_unlock(&idev->info_lock);
    + ret = -EINVAL;
    + goto err_alloc_listener;
    + }
    +
    if (idev->info && idev->info->open)
    ret = idev->info->open(idev->info, inode);
    mutex_unlock(&idev->info_lock);
    @@ -591,6 +632,11 @@ static ssize_t uio_write(struct file *filep, const char __user *buf,
    s32 irq_on;

    mutex_lock(&idev->info_lock);
    + if (!idev->info) {
    + retval = -EINVAL;
    + goto out;
    + }
    +
    if (!idev->info || !idev->info->irq) {
    retval = -EIO;
    goto out;
    @@ -636,10 +682,20 @@ static vm_fault_t uio_vma_fault(struct vm_fault *vmf)
    struct page *page;
    unsigned long offset;
    void *addr;
    + int ret = 0;
    + int mi;

    - int mi = uio_find_mem_index(vmf->vma);
    - if (mi < 0)
    - return VM_FAULT_SIGBUS;
    + mutex_lock(&idev->info_lock);
    + if (!idev->info) {
    + ret = VM_FAULT_SIGBUS;
    + goto out;
    + }
    +
    + mi = uio_find_mem_index(vmf->vma);
    + if (mi < 0) {
    + ret = VM_FAULT_SIGBUS;
    + goto out;
    + }

    /*
    * We need to subtract mi because userspace uses offset = N*PAGE_SIZE
    @@ -654,7 +710,11 @@ static vm_fault_t uio_vma_fault(struct vm_fault *vmf)
    page = vmalloc_to_page(addr);
    get_page(page);
    vmf->page = page;
    - return 0;
    +
    +out:
    + mutex_unlock(&idev->info_lock);
    +
    + return ret;
    }

    static const struct vm_operations_struct uio_logical_vm_ops = {
    @@ -679,6 +739,7 @@ static int uio_mmap_physical(struct vm_area_struct *vma)
    struct uio_device *idev = vma->vm_private_data;
    int mi = uio_find_mem_index(vma);
    struct uio_mem *mem;
    +
    if (mi < 0)
    return -EINVAL;
    mem = idev->info->mem + mi;
    @@ -720,30 +781,46 @@ static int uio_mmap(struct file *filep, struct vm_area_struct *vma)

    vma->vm_private_data = idev;

    + mutex_lock(&idev->info_lock);
    + if (!idev->info) {
    + ret = -EINVAL;
    + goto out;
    + }
    +
    mi = uio_find_mem_index(vma);
    - if (mi < 0)
    - return -EINVAL;
    + if (mi < 0) {
    + ret = -EINVAL;
    + goto out;
    + }

    requested_pages = vma_pages(vma);
    actual_pages = ((idev->info->mem[mi].addr & ~PAGE_MASK)
    + idev->info->mem[mi].size + PAGE_SIZE -1) >> PAGE_SHIFT;
    - if (requested_pages > actual_pages)
    - return -EINVAL;
    + if (requested_pages > actual_pages) {
    + ret = -EINVAL;
    + goto out;
    + }

    if (idev->info->mmap) {
    ret = idev->info->mmap(idev->info, vma);
    - return ret;
    + goto out;
    }

    switch (idev->info->mem[mi].memtype) {
    case UIO_MEM_PHYS:
    - return uio_mmap_physical(vma);
    + ret = uio_mmap_physical(vma);
    + break;
    case UIO_MEM_LOGICAL:
    case UIO_MEM_VIRTUAL:
    - return uio_mmap_logical(vma);
    + ret = uio_mmap_logical(vma);
    + break;
    default:
    - return -EINVAL;
    + ret = -EINVAL;
    }
    +
    +out:
    + mutex_unlock(&idev->info_lock);
    + return 0;
    }

    static const struct file_operations uio_fops = {
    --
    1.8.3.1
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