Hi Wang,
On Wed, Oct 13, 2021 at 07:41:39PM +0800, Wang Hai wrote:
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
Nice simple fix. Applied to drm-misc-next as I did not see the fix as urgent. It will show up in -next in 1-2 weeks.
Sam