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fs: implement kernel_write using __kernel_write 

Consolidate the two in-kernel write helpers to make upcoming changes
easier.  The only difference are the missing call to rw_verify_area
in kernel_write, and an access_ok check that doesn't make sense for
kernel buffers to start with.

Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Christoph Hellwig 2020-05-07 19:33:03 +02:00
parent a01ac27be4
commit 81238b2cff
1 changed files with 9 additions and 8 deletions
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17
fs/read_write.c
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@ -499,6 +499,7 @@ static ssize_t __vfs_write(struct file *file, const char __user *p,
return -EINVAL;
}
/* caller is responsible for file_start_write/file_end_write */
ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t *pos)
{
mm_segment_t old_fs;
@ -528,16 +529,16 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t
ssize_t kernel_write(struct file *file, const void *buf, size_t count,
loff_t *pos)
{
mm_segment_t old_fs;
ssize_t res;
ssize_t ret;
old_fs = get_fs();
set_fs(KERNEL_DS);
/* The cast to a user pointer is valid due to the set_fs() */
res = vfs_write(file, (__force const char __user *)buf, count, pos);
set_fs(old_fs);
ret = rw_verify_area(WRITE, file, pos, count);
if (ret)
return ret;
return res;
file_start_write(file);
ret = __kernel_write(file, buf, count, pos);
file_end_write(file);
return ret;
}
EXPORT_SYMBOL(kernel_write);