[PATCH 11/15] fs: move permission hook out of do_iter_read()

Amir Goldstein
2023-11-14T15:33:18Z

We recently moved fsnotify hook, rw_verify_area() and other checks from
do_iter_write() out to its two callers.

for consistency, do the same thing for do_iter_read() - move the
rw_verify_area() checks and fsnotify hook to the callers vfs_iter_read()
and vfs_readv().

This aligns those vfs helpers with the pattern used in vfs_read() and
vfs_iocb_iter_read() and the vfs write helpers, where all the checks are
in the vfs helpers and the do_* or call_* helpers do the work.

This is needed for fanotify "pre content" events.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
fs/read_write.c | 70 +++++++++++++++++++++++++++++++------------------
1 file changed, 44 insertions(+), 26 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index d4891346d42e..5b18e13c2620 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -781,11 +781,22 @@ static ssize_t do_loop_readv_writev(struct file *filp, struct iov_iter *iter,
}

static ssize_t do_iter_read(struct file *file, struct iov_iter *iter,
- loff_t *pos, rwf_t flags)
+ loff_t *pos, rwf_t flags)
+{
+ if (file->f_op->read_iter)
+ return do_iter_readv_writev(file, iter, pos, READ, flags);
+ else
+ return do_loop_readv_writev(file, iter, pos, READ, flags);
+}
+
+ssize_t vfs_iocb_iter_read(struct file *file, struct kiocb *iocb,
+ struct iov_iter *iter)
{
size_t tot_len;
ssize_t ret = 0;

+ if (!file->f_op->read_iter)
+ return -EINVAL;
if (!(file->f_mode & FMODE_READ))
return -EBADF;
if (!(file->f_mode & FMODE_CAN_READ))
@@ -794,22 +805,20 @@ static ssize_t do_iter_read(struct file *file, struct iov_iter *iter,
tot_len = iov_iter_count(iter);
if (!tot_len)
goto out;
- ret = rw_verify_area(READ, file, pos, tot_len);
+ ret = rw_verify_area(READ, file, &iocb->ki_pos, tot_len);
if (ret < 0)
return ret;

- if (file->f_op->read_iter)
- ret = do_iter_readv_writev(file, iter, pos, READ, flags);
- else
- ret = do_loop_readv_writev(file, iter, pos, READ, flags);
+ ret = call_read_iter(file, iocb, iter);
out:
if (ret >= 0)
fsnotify_access(file);
return ret;
}
+EXPORT_SYMBOL(vfs_iocb_iter_read);

-ssize_t vfs_iocb_iter_read(struct file *file, struct kiocb *iocb,
- struct iov_iter *iter)
+ssize_t vfs_iter_read(struct file *file, struct iov_iter *iter, loff_t *ppos,
+ rwf_t flags)
{
size_t tot_len;
ssize_t ret = 0;
@@ -824,25 +833,16 @@ ssize_t vfs_iocb_iter_read(struct file *file, struct kiocb *iocb,
tot_len = iov_iter_count(iter);
if (!tot_len)
goto out;
- ret = rw_verify_area(READ, file, &iocb->ki_pos, tot_len);
+ ret = rw_verify_area(READ, file, ppos, tot_len);
if (ret < 0)
return ret;

- ret = call_read_iter(file, iocb, iter);
+ ret = do_iter_read(file, iter, ppos, flags);
out:
if (ret >= 0)
fsnotify_access(file);
return ret;
}
-EXPORT_SYMBOL(vfs_iocb_iter_read);
-
-ssize_t vfs_iter_read(struct file *file, struct iov_iter *iter, loff_t *ppos,
- rwf_t flags)
-{
- if (!file->f_op->read_iter)
- return -EINVAL;
- return do_iter_read(file, iter, ppos, flags);
-}
EXPORT_SYMBOL(vfs_iter_read);

static ssize_t do_iter_write(struct file *file, struct iov_iter *iter,
@@ -914,19 +914,37 @@ ssize_t vfs_iter_write(struct file *file, struct iov_iter *iter, loff_t *ppos,
EXPORT_SYMBOL(vfs_iter_write);

static ssize_t vfs_readv(struct file *file, const struct iovec __user *vec,
- unsigned long vlen, loff_t *pos, rwf_t flags)
+ unsigned long vlen, loff_t *pos, rwf_t flags)
{
struct iovec iovstack[UIO_FASTIOV];
struct iovec *iov = iovstack;
struct iov_iter iter;
- ssize_t ret;
+ size_t tot_len;
+ ssize_t ret = 0;

- ret = import_iovec(ITER_DEST, vec, vlen, ARRAY_SIZE(iovstack), &iov, &iter);
- if (ret >= 0) {
- ret = do_iter_read(file, &iter, pos, flags);
- kfree(iov);
- }
+ if (!(file->f_mode & FMODE_READ))
+ return -EBADF;
+ if (!(file->f_mode & FMODE_CAN_READ))
+ return -EINVAL;
+
+ ret = import_iovec(ITER_DEST, vec, vlen, ARRAY_SIZE(iovstack), &iov,
+ &iter);
+ if (ret < 0)
+ return ret;

+ tot_len = iov_iter_count(&iter);
+ if (!tot_len)
+ goto out;
+
+ ret = rw_verify_area(READ, file, pos, tot_len);
+ if (ret < 0)
+ goto out;
+
+ ret = do_iter_read(file, &iter, pos, flags);
+out:
+ if (ret >= 0)
+ fsnotify_access(file);
+ kfree(iov);
return ret;
}

--
2.34.1