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Subject[PATCH 11/11] fs: don't allow splice read/write without explicit ops
Date
Now that __kernel_write or __kernel_write don't just work on all
file operations instances there is not much of a point of providing
default splice methods. Renamed the existing default ones to
simple_ and wire them up for the few instancas actually implementing
->read_uptr and ->write_uptr.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/proc/proc_sysctl.c | 2 ++
fs/splice.c | 40 ++++++++++++++++++++++++++++------------
include/linux/fs.h | 5 ++++-
3 files changed, 34 insertions(+), 13 deletions(-)

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index dd5eb693bd00df..5adbc1c8f899cd 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -856,6 +856,8 @@ static const struct file_operations proc_sys_file_operations = {
.poll = proc_sys_poll,
.read_uptr = proc_sys_read,
.write_uptr = proc_sys_write,
+ .splice_read = simple_splice_read,
+ .splice_write = simple_splice_write,
.llseek = default_llseek,
};

diff --git a/fs/splice.c b/fs/splice.c
index d1efc53875bd93..d5bba2cd695b5d 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -342,9 +342,8 @@ const struct pipe_buf_operations nosteal_pipe_buf_ops = {
};
EXPORT_SYMBOL(nosteal_pipe_buf_ops);

-static ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
- struct pipe_inode_info *pipe, size_t len,
- unsigned int flags)
+ssize_t simple_splice_read(struct file *in, loff_t *ppos,
+ struct pipe_inode_info *pipe, size_t len, unsigned int flags)
{
struct iov_iter to;
struct page **pages;
@@ -779,9 +778,8 @@ static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
return ret;
}

-static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
- struct file *out, loff_t *ppos,
- size_t len, unsigned int flags)
+ssize_t simple_splice_write(struct pipe_inode_info *pipe, struct file *out,
+ loff_t *ppos, size_t len, unsigned int flags)
{
ssize_t ret;

@@ -813,15 +811,30 @@ ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,

EXPORT_SYMBOL(generic_splice_sendpage);

+static void warn_unsupported(struct file *file, const char *op)
+{
+ char pathname[128], *path;
+
+ path = file_path(file, pathname, sizeof(pathname));
+ if (IS_ERR(path))
+ path = "(unknown)";
+ pr_debug_ratelimited(
+ "splice %s not supported for file %s (pid: %d comm: %.20s)\n",
+ op, path, current->pid, current->comm);
+}
+
/*
* Attempt to initiate a splice from pipe to file.
*/
static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
loff_t *ppos, size_t len, unsigned int flags)
{
- if (out->f_op->splice_write)
- return out->f_op->splice_write(pipe, out, ppos, len, flags);
- return default_file_splice_write(pipe, out, ppos, len, flags);
+ if (!out->f_op->splice_write) {
+ warn_unsupported(out, "write");
+ return -EINVAL;
+ }
+
+ return out->f_op->splice_write(pipe, out, ppos, len, flags);
}

/*
@@ -843,9 +856,12 @@ static long do_splice_to(struct file *in, loff_t *ppos,
if (unlikely(len > MAX_RW_COUNT))
len = MAX_RW_COUNT;

- if (in->f_op->splice_read)
- return in->f_op->splice_read(in, ppos, pipe, len, flags);
- return default_file_splice_read(in, ppos, pipe, len, flags);
+ if (!in->f_op->splice_read) {
+ warn_unsupported(in, "read");
+ return -EINVAL;
+ }
+
+ return in->f_op->splice_read(in, ppos, pipe, len, flags);
}

/**
diff --git a/include/linux/fs.h b/include/linux/fs.h
index d0fea0281ef29b..64a6506cba0446 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3175,7 +3175,10 @@ extern ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe,
struct file *out, loff_t *, size_t len, unsigned int flags);
extern long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
loff_t *opos, size_t len, unsigned int flags);
-
+ssize_t simple_splice_read(struct file *in, loff_t *ppos,
+ struct pipe_inode_info *pipe, size_t len, unsigned int flags);
+ssize_t simple_splice_write(struct pipe_inode_info *pipe, struct file *out,
+ loff_t *ppos, size_t len, unsigned int flags);

extern void
file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping);
--
2.26.2
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