[PATCH 21/23] fs: don't allow kernel reads and writes without iter ops

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Don't allow calling ->read or ->write with set_fs as a preparation for
killing off set_fs.  While I've not triggered any of these cases in my
setups as all the usual suspect (file systems, pipes, sockets, block
devices, system character devices) use the iter ops this is almost
going to be guaranteed to eventuall break something, so print a detailed
error message helping to debug such cases.  The fix will be to switch the
affected driver to use the iter ops.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 fs/read_write.c | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 7550c195a6a10e..2a2e4efed47395 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -420,6 +420,13 @@ ssize_t iter_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos,
 	return ret;
 }
 
+static void warn_unsupported(struct file *file, const char *op)
+{
+	pr_warn_ratelimited(
+		"kernel %s not supported for file %pD4 (pid: %d comm: %.20s)\n",
+		op, file, current->pid, current->comm);
+}
+
 ssize_t __kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)
 {
 	ssize_t ret;
@@ -431,13 +438,7 @@ ssize_t __kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)
 
 	if (count > MAX_RW_COUNT)
 		count =  MAX_RW_COUNT;
-	if (file->f_op->read) {
-		mm_segment_t old_fs = get_fs();
-
-		set_fs(KERNEL_DS);
-		ret = file->f_op->read(file, (void __user *)buf, count, pos);
-		set_fs(old_fs);
-	} else if (file->f_op->read_iter) {
+	if (file->f_op->read_iter) {
 		struct kvec iov = { .iov_base = buf, .iov_len = count };
 		struct kiocb kiocb;
 		struct iov_iter iter;
@@ -448,6 +449,8 @@ ssize_t __kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)
 		ret = file->f_op->read_iter(&kiocb, &iter);
 		*pos = kiocb.ki_pos;
 	} else {
+		if (file->f_op->read)
+			warn_unsupported(file, "read");
 		ret = -EINVAL;
 	}
 	if (ret > 0) {
@@ -532,14 +535,7 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count,
 
 	if (count > MAX_RW_COUNT)
 		count =  MAX_RW_COUNT;
-	if (file->f_op->write) {
-		mm_segment_t old_fs = get_fs();
-
-		set_fs(KERNEL_DS);
-		ret = file->f_op->write(file, (__force const char __user *)buf,
-				count, pos);
-		set_fs(old_fs);
-	} else if (file->f_op->write_iter) {
+	if (file->f_op->write_iter) {
 		struct kvec iov = { .iov_base = (void *)buf, .iov_len = count };
 		struct kiocb kiocb;
 		struct iov_iter iter;
@@ -551,6 +547,8 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count,
 		if (ret > 0)
 			*pos = kiocb.ki_pos;
 	} else {
+		if (file->f_op->write)
+			warn_unsupported(file, "write");
 		ret = -EINVAL;
 	}
 	if (ret > 0) {
-- 
2.26.2




[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [Samba]     [Device Mapper]     [CEPH Development]

  Powered by Linux