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Tsirkin" To: Greg KH Cc: Xie Yongji , jasowang@redhat.com, mcgrof@kernel.org, akpm@linux-foundation.org, oliver.sang@intel.com, virtualization@lists.linux-foundation.org, stable@vger.kernel.org Subject: Re: [PATCH v2] vduse: Fix NULL pointer dereference on sysfs access Message-ID: <20220608085133-mutt-send-email-mst@kernel.org> References: <20220426073656.229-1-xieyongji@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Tue, Apr 26, 2022 at 10:07:38AM +0200, Greg KH wrote: > On Tue, Apr 26, 2022 at 03:36:56PM +0800, Xie Yongji wrote: > > The control device has no drvdata. So we will get a > > NULL pointer dereference when accessing control > > device's msg_timeout attribute via sysfs: > > > > [ 132.841881][ T3644] BUG: kernel NULL pointer dereference, address: 00000000000000f8 > > [ 132.850619][ T3644] RIP: 0010:msg_timeout_show (drivers/vdpa/vdpa_user/vduse_dev.c:1271) > > [ 132.869447][ T3644] dev_attr_show (drivers/base/core.c:2094) > > [ 132.870215][ T3644] sysfs_kf_seq_show (fs/sysfs/file.c:59) > > [ 132.871164][ T3644] ? device_remove_bin_file (drivers/base/core.c:2088) > > [ 132.872082][ T3644] kernfs_seq_show (fs/kernfs/file.c:164) > > [ 132.872838][ T3644] seq_read_iter (fs/seq_file.c:230) > > [ 132.873578][ T3644] ? __vmalloc_area_node (mm/vmalloc.c:3041) > > [ 132.874532][ T3644] kernfs_fop_read_iter (fs/kernfs/file.c:238) > > [ 132.875513][ T3644] __kernel_read (fs/read_write.c:440 (discriminator 1)) > > [ 132.876319][ T3644] kernel_read (fs/read_write.c:459) > > [ 132.877129][ T3644] kernel_read_file (fs/kernel_read_file.c:94) > > [ 132.877978][ T3644] kernel_read_file_from_fd (include/linux/file.h:45 fs/kernel_read_file.c:186) > > [ 132.879019][ T3644] __do_sys_finit_module (kernel/module.c:4207) > > [ 132.879930][ T3644] __ia32_sys_finit_module (kernel/module.c:4189) > > [ 132.880930][ T3644] do_int80_syscall_32 (arch/x86/entry/common.c:112 arch/x86/entry/common.c:132) > > [ 132.881847][ T3644] entry_INT80_compat (arch/x86/entry/entry_64_compat.S:419) > > > > To fix it, don't create the unneeded attribute for > > control device anymore. > > > > Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace") > > Reported-by: kernel test robot > > Cc: stable@vger.kernel.org > > Signed-off-by: Xie Yongji > > --- > > drivers/vdpa/vdpa_user/vduse_dev.c | 7 +++---- > > 1 file changed, 3 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c > > index f85d1a08ed87..160e40d03084 100644 > > --- a/drivers/vdpa/vdpa_user/vduse_dev.c > > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c > > @@ -1344,9 +1344,9 @@ static int vduse_create_dev(struct vduse_dev_config *config, > > > > dev->minor = ret; > > dev->msg_timeout = VDUSE_MSG_DEFAULT_TIMEOUT; > > - dev->dev = device_create(vduse_class, NULL, > > - MKDEV(MAJOR(vduse_major), dev->minor), > > - dev, "%s", config->name); > > + dev->dev = device_create_with_groups(vduse_class, NULL, > > + MKDEV(MAJOR(vduse_major), dev->minor), > > + dev, vduse_dev_groups, "%s", config->name); > > if (IS_ERR(dev->dev)) { > > ret = PTR_ERR(dev->dev); > > goto err_dev; > > @@ -1595,7 +1595,6 @@ static int vduse_init(void) > > return PTR_ERR(vduse_class); > > > > vduse_class->devnode = vduse_devnode; > > - vduse_class->dev_groups = vduse_dev_groups; > > Ok, this looks much better. > > But wow, there are some problems in this code overall. I see a number > of flat-out-wrong things in there that should have been caught by code > reviews. Some examples: > - empty release() callbacks. That is a huge sign the code > design is wrong and broken and you are just trying to make the > driver core quiet for some reason. The documentation in the > kernel explains why this is not ok. > - __module_get(THIS_MODULE); That's racy, buggy, and doesn't do > what you think it does. Please never ever ever do that. It > too is a sign of a broken design. > - no Documentation/ABI/ entries for the sysfs files here. I > think it's burried in some other documentation file but that's > not the correct place for it and if you run scripts/get_abi.pl > with the code loaded it will rightly complain about this. > > Do you want to address these, or do you want patches for them? > > thanks, > > greg k-h So, any patches? -- MST