fs: move permission hook out of do_iter_read()

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>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/r/20231122122715.2561213-13-amir73il@gmail.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/read_write.c b/fs/read_write.c
index d08d0a3ff7dec72a6e7ca1e2d79a2391f6e18797..9fce8d6968df6fccf6feaaf812bb6b6e9b31f949 100644 (file)
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -773,12 +773,14 @@ static ssize_t do_loop_readv_writev(struct file *filp, struct iov_iter *iter,
        return ret;
 }
 
-static ssize_t do_iter_read(struct file *file, struct iov_iter *iter,
-               loff_t *pos, rwf_t 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))
@@ -787,22 +789,20 @@ 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;
@@ -817,25 +817,16 @@ 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_readv_writev(file, iter, ppos, READ, 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);
 
 ssize_t vfs_iocb_iter_write(struct file *file, struct kiocb *iocb,
@@ -898,19 +889,40 @@ 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;
 
+       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);
+out:
+       if (ret >= 0)
+               fsnotify_access(file);
+       kfree(iov);
        return ret;
 }