On Tue, Jan 19, 2021 at 03:25:10PM +0530, Shradha Todi wrote: > > -----Original Message----- > > From: Leon Romanovsky <leon@xxxxxxxxxx> > > Subject: Re: [PATCH v4] PCI: endpoint: Fix NULL pointer dereference for - > > >get_features() > > > > On Tue, Jan 12, 2021 at 07:32:25PM +0530, Shradha Todi wrote: > > > get_features ops of pci_epc_ops may return NULL, causing NULL pointer > > > dereference in pci_epf_test_bind function. Let us add a check for > > > pci_epc_feature pointer in pci_epf_test_bind before we access it to > > > avoid any such NULL pointer dereference and return -ENOTSUPP in case > > > pci_epc_feature is not found. > > > > > > When the patch is not applied and EPC features is not implemented in > > > the platform driver, we see the following dump due to kernel NULL > > > pointer dereference. > > > > > > [ 105.135936] Call trace: > > > [ 105.138363] pci_epf_test_bind+0xf4/0x388 [ 105.142354] > > > pci_epf_bind+0x3c/0x80 [ 105.145817] pci_epc_epf_link+0xa8/0xcc [ > > > 105.149632] configfs_symlink+0x1a4/0x48c [ 105.153616] > > > vfs_symlink+0x104/0x184 [ 105.157169] do_symlinkat+0x80/0xd4 [ > > > 105.160636] __arm64_sys_symlinkat+0x1c/0x24 [ 105.164885] > > > el0_svc_common.constprop.3+0xb8/0x170 > > > [ 105.169649] el0_svc_handler+0x70/0x88 [ 105.173377] > > > el0_svc+0x8/0x640 [ 105.176411] Code: d2800581 b9403ab9 f9404ebb > > > 8b394f60 (f9400400) [ 105.182478] ---[ end trace a438e3c5a24f9df0 > > > ]--- > > > > > > Description and call trace don't correlate with the proposed code change. > > > > The code in pci_epf_test_bind() doesn't dereference epc_features, at least > in > > direct manner. > > > > Thanks > > Thanks for the review. Yes, you're right. The dereference does not happen in > the pci_epf_test_bind() itself, but in pci_epf_test_alloc_space() being > called within. We will update the line "causing NULL pointer dereference in > pci_epf_test_bind function. " in the commit message to "causing NULL pointer > dereference in pci_epf_test_alloc_space function. " Would that be good > enough? I have no idea, just saw that the rest of the code at least partially prepared to deal with epc_features == NULL, maybe pci_epf_test_alloc_space() should be update to handle epc_features == NULL. Thanks >
