I got a null-ptr-deref report:
BUG: kernel NULL pointer dereference, address: 0000000000000030 ... RIP: 0010:kobject_put+0x2a/0x180 ... Call Trace: put_device+0x25/0x30 drm_minor_alloc_release.cold+0x45/0x7f [drm] drm_managed_release+0x158/0x2d0 [drm] drm_dev_init+0x3a7/0x4a0 [drm] __devm_drm_dev_alloc+0x55/0xd0 [drm] mi0283qt_probe+0x8a/0x2b5 [mi0283qt] spi_probe+0xeb/0x130 ... entry_SYSCALL_64_after_hwframe+0x44/0xae
If drm_sysfs_minor_alloc() fails in drm_minor_alloc(), minor->kdev will point to PTR_ERR(...) instead of NULL. This will result in null-ptr-deref when put_device(minor->kdev) is called.
drm_dev_init() drm_minor_alloc() drm_sysfs_minor_alloc(); // fail, minor->kdev = PTR_ERR(...) drm_managed_release() drm_minor_alloc_release() put_device(minor->kdev); // access non-existent kdev
Define a temp variable and assign it to minor->kdev if the temp variable is not PTR_ERR.
Fixes: f96306f9892b ("drm: manage drm_minor cleanup with drmm_") Reported-by: Hulk Robot hulkci@huawei.com Signed-off-by: Wang Hai wanghai38@huawei.com --- drivers/gpu/drm/drm_drv.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index b3a1636d1b98..b302536edbce 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -112,6 +112,7 @@ static int drm_minor_alloc(struct drm_device *dev, unsigned int type) { struct drm_minor *minor; unsigned long flags; + struct device *kdev; int r;
minor = drmm_kzalloc(dev, sizeof(*minor), GFP_KERNEL); @@ -140,9 +141,11 @@ static int drm_minor_alloc(struct drm_device *dev, unsigned int type) if (r) return r;
- minor->kdev = drm_sysfs_minor_alloc(minor); - if (IS_ERR(minor->kdev)) - return PTR_ERR(minor->kdev); + kdev = drm_sysfs_minor_alloc(minor); + if (IS_ERR(kdev)) + return PTR_ERR(kdev); + + minor->kdev = kdev;
*drm_minor_get_slot(dev, type) = minor; return 0;