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fs: move permission hook out of do_iter_write()

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In many of the vfs helpers, the rw_verity_area() checks are called before
taking sb_start_write(), making them "start-write-safe".
do_iter_write() is an exception to this rule.

do_iter_write() has two callers - vfs_iter_write() and vfs_writev().
Move rw_verify_area() and other checks from do_iter_write() out to
its callers to make them "start-write-safe".

Move also the fsnotify_modify() hook to align with similar pattern
used in vfs_write() and other vfs helpers.

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/20231122122715.2561213-12-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>
This commit is contained in:
Amir Goldstein 2023-07-16 14:47:14 +03:00 committed by Christian Brauner
parent 269aed7014
commit 1c8aa83303
1 changed files with 48 additions and 38 deletions
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86
fs/read_write.c
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@ -838,33 +838,6 @@ ssize_t vfs_iter_read(struct file *file, struct iov_iter *iter, loff_t *ppos,
}
EXPORT_SYMBOL(vfs_iter_read);
static ssize_t do_iter_write(struct file *file, struct iov_iter *iter,
loff_t *pos, rwf_t flags)
{
size_t tot_len;
ssize_t ret = 0;
if (!(file->f_mode & FMODE_WRITE))
return -EBADF;
if (!(file->f_mode & FMODE_CAN_WRITE))
return -EINVAL;
tot_len = iov_iter_count(iter);
if (!tot_len)
return 0;
ret = rw_verify_area(WRITE, file, pos, tot_len);
if (ret < 0)
return ret;
if (file->f_op->write_iter)
ret = do_iter_readv_writev(file, iter, pos, WRITE, flags);
else
ret = do_loop_readv_writev(file, iter, pos, WRITE, flags);
if (ret > 0)
fsnotify_modify(file);
return ret;
}
ssize_t vfs_iocb_iter_write(struct file *file, struct kiocb *iocb,
struct iov_iter *iter)
{
@ -896,13 +869,28 @@ EXPORT_SYMBOL(vfs_iocb_iter_write);
ssize_t vfs_iter_write(struct file *file, struct iov_iter *iter, loff_t *ppos,
rwf_t flags)
{
int ret;
size_t tot_len;
ssize_t ret;
if (!(file->f_mode & FMODE_WRITE))
return -EBADF;
if (!(file->f_mode & FMODE_CAN_WRITE))
return -EINVAL;
if (!file->f_op->write_iter)
return -EINVAL;
tot_len = iov_iter_count(iter);
if (!tot_len)
return 0;
ret = rw_verify_area(WRITE, file, ppos, tot_len);
if (ret < 0)
return ret;
file_start_write(file);
ret = do_iter_write(file, iter, ppos, flags);
ret = do_iter_readv_writev(file, iter, ppos, WRITE, flags);
if (ret > 0)
fsnotify_modify(file);
file_end_write(file);
return ret;
@ -927,20 +915,42 @@ static ssize_t vfs_readv(struct file *file, const struct iovec __user *vec,
}
static ssize_t vfs_writev(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_SOURCE, vec, vlen, ARRAY_SIZE(iovstack), &iov, &iter);
if (ret >= 0) {
file_start_write(file);
ret = do_iter_write(file, &iter, pos, flags);
file_end_write(file);
kfree(iov);
}
if (!(file->f_mode & FMODE_WRITE))
return -EBADF;
if (!(file->f_mode & FMODE_CAN_WRITE))
return -EINVAL;
ret = import_iovec(ITER_SOURCE, 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(WRITE, file, pos, tot_len);
if (ret < 0)
goto out;
file_start_write(file);
if (file->f_op->write_iter)
ret = do_iter_readv_writev(file, &iter, pos, WRITE, flags);
else
ret = do_loop_readv_writev(file, &iter, pos, WRITE, flags);
if (ret > 0)
fsnotify_modify(file);
file_end_write(file);
out:
kfree(iov);
return ret;
}