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Date:   Tue, 15 Sep 2020 14:55:30 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "io-uring@...r.kernel.org" <io-uring@...r.kernel.org>,
        Jens Axboe <axboe@...nel.dk>,
        "David S. Miller" <davem@...emloft.net>,
        Al Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: [PATCH 7/9 next] mm/process_vm_access: Use iovec_import() instead of
 import_iovec().

iovec_import() has a safer calling convention than import_iovec().

Signed-off-by: David Laight <david.laight@...lab.com>
---
 mm/process_vm_access.c | 81 ++++++++++++++++++++++--------------------
 1 file changed, 42 insertions(+), 39 deletions(-)

diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
index 1cc3d6f66b31..048637944d47 100644
--- a/mm/process_vm_access.c
+++ b/mm/process_vm_access.c
@@ -260,10 +260,10 @@ static ssize_t process_vm_rw(pid_t pid,
 			     unsigned long riovcnt,
 			     unsigned long flags, int vm_write)
 {
-	struct iovec iovstack_l[UIO_FASTIOV];
-	struct iovec iovstack_r[UIO_FASTIOV];
-	struct iovec *iov_l = iovstack_l;
-	struct iovec *iov_r = iovstack_r;
+	struct iovec_cache cache_l;
+	struct iovec_cache cache_r;
+	struct iovec *iov_l;
+	struct iovec *iov_r;
 	struct iov_iter iter_l, iter_r;
 	ssize_t rc;
 	int dir = vm_write ? WRITE : READ;
@@ -272,24 +272,25 @@ static ssize_t process_vm_rw(pid_t pid,
 		return -EINVAL;
 
 	/* Check iovecs */
-	rc = import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter_l);
-	if (rc < 0)
-		return rc;
-	if (!iov_iter_count(&iter_l))
-		goto free_iovecs;
-
-	rc = import_iovec(CHECK_IOVEC_ONLY, rvec, riovcnt, UIO_FASTIOV, &iov_r, &iter_r);
-	if (rc <= 0)
-		goto free_iovecs;
-
-	rc = process_vm_rw_core(pid, &iter_l, iter_r.iov, iter_r.nr_segs,
-				flags, vm_write);
+	iov_l = iovec_import(dir, lvec, liovcnt, &cache_l, &iter_l);
+	if (IS_ERR(iov_l))
+		return PTR_ERR(iov_l);
+	if (!iov_iter_count(&iter_l)) {
+		rc = 0;
+		goto free_iovec_l;
+	}
 
-free_iovecs:
-	if (iov_r != iovstack_r)
+	iov_r = iovec_import(CHECK_IOVEC_ONLY, rvec, riovcnt, &cache_r, &iter_r);
+	if (IS_ERR(iov_r)) {
+		rc = PTR_ERR(iov_r);
+	} else {
+		rc = process_vm_rw_core(pid, &iter_l, iter_r.iov,
+				iter_r.nr_segs, flags, vm_write);
 		kfree(iov_r);
-	if (iov_l != iovstack_l)
-		kfree(iov_l);
+	}
+
+free_iovec_l:
+	kfree(iov_l);
 
 	return rc;
 }
@@ -319,10 +320,10 @@ compat_process_vm_rw(compat_pid_t pid,
 		     unsigned long riovcnt,
 		     unsigned long flags, int vm_write)
 {
-	struct iovec iovstack_l[UIO_FASTIOV];
-	struct iovec iovstack_r[UIO_FASTIOV];
-	struct iovec *iov_l = iovstack_l;
-	struct iovec *iov_r = iovstack_r;
+	struct iovec_cache cache_l;
+	struct iovec_cache cache_r;
+	struct iovec *iov_l;
+	struct iovec *iov_r;
 	struct iov_iter iter_l, iter_r;
 	ssize_t rc = -EFAULT;
 	int dir = vm_write ? WRITE : READ;
@@ -330,23 +331,25 @@ compat_process_vm_rw(compat_pid_t pid,
 	if (flags != 0)
 		return -EINVAL;
 
-	rc = compat_import_iovec(dir, lvec, liovcnt, UIO_FASTIOV, &iov_l, &iter_l);
-	if (rc < 0)
-		return rc;
-	if (!iov_iter_count(&iter_l))
-		goto free_iovecs;
-	rc = compat_import_iovec(0, rvec, riovcnt, UIO_FASTIOV, &iov_r, &iter_r);
-	if (rc <= 0)
-		goto free_iovecs;
-
-	rc = process_vm_rw_core(pid, &iter_l, iter_r.iov, iter_r.nr_segs,
-				flags, vm_write);
+	iov_l = compat_iovec_import(dir, lvec, liovcnt, &cache_l, &iter_l);
+	if (IS_ERR(iov_l))
+		return PTR_ERR(iov_l);
+	if (!iov_iter_count(&iter_l)) {
+		rc = 0;
+		goto free_iovec_l;
+	}
 
-free_iovecs:
-	if (iov_r != iovstack_r)
+	iov_r = compat_iovec_import(0, rvec, riovcnt, &cache_r, &iter_r);
+	if (IS_ERR(iov_r)) {
+		rc = PTR_ERR(iov_r);
+	} else {
+		rc = process_vm_rw_core(pid, &iter_l, iter_r.iov,
+				iter_r.nr_segs, flags, vm_write);
 		kfree(iov_r);
-	if (iov_l != iovstack_l)
-		kfree(iov_l);
+	}
+
+free_iovec_l:
+	kfree(iov_l);
 	return rc;
 }
 
-- 
2.25.1

-
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