From: Jason Gunthorpe <jgg@nvidia.com>
Date: Tue, 3 Mar 2026 19:50:02 +0000 (-0400)
Subject: RDMA: Add ib_respond_udata()
X-Git-Tag: v7.1-rc1~75^2~73
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=14badc323ed7153c24a0a9c3175e594aaf1366c9;p=thirdparty%2Fkernel%2Flinux.git

RDMA: Add ib_respond_udata()

Wrap the common copy_to_user() pattern used in drivers and enhance it
to zero pad as well. Include debug logging on failures.

Link: https://patch.msgid.link/r/5-v3-bd56dd443069+49-bnxt_re_uapi_jgg@nvidia.com
Tested-by: Sriharsha Basavapatna <sriharsha.basavapatna@broadcom.com>
Acked-by: Sriharsha Basavapatna <sriharsha.basavapatna@broadcom.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---

diff --git a/drivers/infiniband/core/uverbs_ioctl.c b/drivers/infiniband/core/uverbs_ioctl.c
index 5e5b00c6236f..b61af625e679 100644
--- a/drivers/infiniband/core/uverbs_ioctl.c
+++ b/drivers/infiniband/core/uverbs_ioctl.c
@@ -910,3 +910,27 @@ int _ib_copy_validate_udata_cm_fail(struct ib_udata *udata, u64 req_cm,
 	return -EOPNOTSUPP;
 }
 EXPORT_SYMBOL(_ib_copy_validate_udata_cm_fail);
+
+int _ib_respond_udata(struct ib_udata *udata, const void *src, size_t len)
+{
+	size_t copy_len;
+
+	/* 0 length copy_len is a NOP for copy_to_user() and doesn't fail. */
+	copy_len = min(len, udata->outlen);
+	if (copy_to_user(udata->outbuf, src, copy_len))
+		goto err_fault;
+	if (copy_len < udata->outlen) {
+		if (clear_user(udata->outbuf + copy_len,
+			       udata->outlen - copy_len))
+			goto err_fault;
+	}
+	return 0;
+err_fault:
+	ibdev_dbg(
+		rdma_udata_to_dev(udata),
+		"System call driver out udata has EFAULT (%zu into %zu) for ioctl %ps called by %pSR\n",
+		len, udata->outlen, uverbs_get_handler_fn(udata),
+		__builtin_return_address(0));
+	return -EFAULT;
+}
+EXPORT_SYMBOL(_ib_respond_udata);
diff --git a/include/rdma/uverbs_ioctl.h b/include/rdma/uverbs_ioctl.h
index a73016a977a1..38a11bfe1374 100644
--- a/include/rdma/uverbs_ioctl.h
+++ b/include/rdma/uverbs_ioctl.h
@@ -900,6 +900,7 @@ int uverbs_copy_to_struct_or_zero(const struct uverbs_attr_bundle *bundle,
 
 int _ib_copy_validate_udata_in(struct ib_udata *udata, void *req,
 			       size_t kernel_size, size_t minimum_size);
+int _ib_respond_udata(struct ib_udata *udata, const void *src, size_t len);
 #else
 static inline int
 uverbs_get_flags64(u64 *to, const struct uverbs_attr_bundle *attrs_bundle,
@@ -964,6 +965,11 @@ static inline int _ib_copy_validate_udata_in(struct ib_udata *udata, void *req,
 	return -EINVAL;
 }
 
+static inline int _ib_respond_udata(struct ib_udata *udata, const void *src,
+				    size_t len)
+{
+	return -EINVAL;
+}
 #endif
 
 #define uverbs_get_const_signed(_to, _attrs_bundle, _idx)                      \
@@ -1069,4 +1075,31 @@ int _ib_copy_validate_udata_cm_fail(struct ib_udata *udata, u64 req_cm,
 		ret;                                                          \
 	})
 
+/**
+ * ib_respond_udata - Copy a driver data response to userspace
+ * @_udata: The system calls ib_udata struct
+ * @_rep: Kernel buffer containing the response driver data on the stack
+ *
+ * Copy driver data response structures back to userspace in a way that
+ * is forwards and backwards compatible. Longer kernel structs are truncated,
+ * userspace has made some kind of error if it needed the truncated information.
+ * Shorter structs are zero padded.
+ */
+#define ib_respond_udata(_udata, _rep) \
+	_ib_respond_udata(_udata, &(_rep), sizeof(_rep))
+
+/**
+ * ib_respond_empty_udata - Zero fill the response buffer to userspace
+ * @_udata: The system calls ib_udata struct
+ *
+ * Used when there is no driver response data to return. Provides forward
+ * compatability by zeroing any buffer the user may have provided.
+ */
+static inline int ib_respond_empty_udata(struct ib_udata *udata)
+{
+	if (udata && udata->outlen && clear_user(udata->outbuf, udata->outlen))
+		return -EFAULT;
+	return 0;
+}
+
 #endif