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Sashiko AI review found 1 potential issue(s) to consider: > > Pre-existing issues: > - [Critical] Missing validation of the user-provided `in_len` parameter allows a `ZERO_SIZE_PTR` dereference and severe out-of-bounds reads in the CXL FWCTL driver. > -- > > commit 149380dfe9472c578ca9fd76d4e5bb0c5ac85c19 > Author: Richard Cheng > > cxl/features: Reject Set Features output buffer smaller than the header > > cxlctl_set_feature() sizes its output buffer from the user's > fwctl_rpc.out_len but never checks it is large enough to hold even the > fwctl_rpc_cxl_out header. With out_len == 0 , kvzalloc() returns > ZERO_SIZE_PTR, which passes the !rpc_out check, the subsequent > rpc_out->size = 0 then writes through the poison pointer. > > > diff --git a/drivers/cxl/core/features.c b/drivers/cxl/core/features.c > > index 9c714ee42a411..ed18ccb5e236e 100644 > > --- a/drivers/cxl/core/features.c > > +++ b/drivers/cxl/core/features.c > > @@ -520,6 +520,9 @@ static void *cxlctl_set_feature(struct cxl_features_state *cxlfs, > > flags = le32_to_cpu(feat_in->flags); > > out_size = *out_len; > > > > + if (out_size < offsetof(struct fwctl_rpc_cxl_out, payload)) > > + return ERR_PTR(-EINVAL); > > + > > [Severity: Critical] > This is a pre-existing issue, but missing validation of the user-provided > in_len parameter allows a ZERO_SIZE_PTR dereference and out-of-bounds reads. > > If a malicious user passes in_len=0 to the FWCTL_RPC ioctl, kvzalloc(0) > returns the ZERO_SIZE_PTR constant (0x10) in > drivers/fwctl/main.c:fwctl_cmd_rpc(): > > void *inbuf __free(kvfree) = kvzalloc(cmd->in_len, GFP_KERNEL_ACCOUNT); > > The driver unconditionally dereferences this pointer in > drivers/cxl/core/features.c:cxlctl_fw_rpc(): > > const struct fwctl_rpc_cxl *rpc_in = in; > u16 opcode = rpc_in->opcode; > > Also, if a user provides a small in_len but specifies a massive op_size in > the command header, handlers like cxlctl_set_feature() will read out of > bounds of the kvzalloc'd heap buffer and transmit that data to the hardware > mailbox: > > data_size = rpc_in->op_size - sizeof(feat_in->hdr); > rc = cxl_set_feature(cxl_mbox, &feat_in->uuid, > feat_in->version, feat_in->feat_data, > data_size, flags, offset, &return_code); > > Should there be validation of in_len before casting and accessing the input > buffer, as well as a check to ensure rpc_in->op_size does not exceed in_len? > > > struct fwctl_rpc_cxl_out *rpc_out __free(kvfree) = > > kvzalloc(out_size, GFP_KERNEL); > > if (!rpc_out) > > -- > Sashiko AI review · https://sashiko.dev/#/patchset/20260626104102.53892-1-icheng@nvidia.com?part=2 Same as the previous one, addressed here https://lore.kernel.org/linux-cxl/20260620-cxl-fwctl-oob-v1-1-5758e34d784a@gmail.com/ --Richard