From: Wang Hai wanghai38@huawei.com
[ Upstream commit acf20ed020ffa4d6cc8347e8d356509b95df3cbe ]
I got a null-ptr-deref report:
[drm:drm_dev_init [drm]] *ERROR* Cannot allocate anonymous inode: -12 ================================================================== BUG: KASAN: null-ptr-deref in iput+0x3c/0x4a0 ... Call Trace: dump_stack_lvl+0x6c/0x8b kasan_report.cold+0x64/0xdb __asan_load8+0x69/0x90 iput+0x3c/0x4a0 drm_dev_init_release+0x39/0xb0 [drm] drm_managed_release+0x158/0x2d0 [drm] drm_dev_init+0x3a7/0x4c0 [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_fs_inode_new() fails in drm_dev_init(), dev->anon_inode will point to PTR_ERR(...) instead of NULL. This will result in null-ptr-deref when drm_fs_inode_free(dev->anon_inode) is called.
drm_dev_init() drm_fs_inode_new() // fail, dev->anon_inode = PTR_ERR(...) drm_managed_release() drm_dev_init_release() drm_fs_inode_free() // access non-existent anon_inode
Define a temp variable and assign it to dev->anon_inode if the temp variable is not PTR_ERR.
Fixes: 2cbf7fc6718b ("drm: Use drmm_ for drm_dev_init cleanup") Reported-by: Hulk Robot hulkci@huawei.com Signed-off-by: Wang Hai wanghai38@huawei.com Signed-off-by: Sam Ravnborg sam@ravnborg.org Link: https://patchwork.freedesktop.org/patch/msgid/20211013114139.4042207-1-wangh... Signed-off-by: Sasha Levin sashal@kernel.org --- 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 cd162d406078a..006e3b896caea 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -577,6 +577,7 @@ static int drm_dev_init(struct drm_device *dev, struct drm_driver *driver, struct device *parent) { + struct inode *inode; int ret;
if (!drm_core_init_complete) { @@ -613,13 +614,15 @@ static int drm_dev_init(struct drm_device *dev, if (ret) return ret;
- dev->anon_inode = drm_fs_inode_new(); - if (IS_ERR(dev->anon_inode)) { - ret = PTR_ERR(dev->anon_inode); + inode = drm_fs_inode_new(); + if (IS_ERR(inode)) { + ret = PTR_ERR(inode); DRM_ERROR("Cannot allocate anonymous inode: %d\n", ret); goto err; }
+ dev->anon_inode = inode; + if (drm_core_check_feature(dev, DRIVER_RENDER)) { ret = drm_minor_alloc(dev, DRM_MINOR_RENDER); if (ret)