[PATCH v7 2/4] fs/proc/kcore: convert read_kcore() to read_kcore_iter()

Lorenzo Stoakes
2023-03-22T18:57:15Z

For the time being we still use a bounce buffer for vread(), however in the
next patch we will convert this to interact directly with the iterator and
eliminate the bounce buffer altogether.

Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
---
fs/proc/kcore.c | 36 ++++++++++++++++++------------------
1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index 556f310d6aa4..08b795fd80b4 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -24,7 +24,7 @@
#include <linux/memblock.h>
#include <linux/init.h>
#include <linux/slab.h>
-#include <linux/uaccess.h>
+#include <linux/uio.h>
#include <asm/io.h>
#include <linux/list.h>
#include <linux/ioport.h>
@@ -308,9 +308,12 @@ static void append_kcore_note(char *notes, size_t *i, const char *name,
}

static ssize_t
-read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
+read_kcore_iter(struct kiocb *iocb, struct iov_iter *iter)
{
+ struct file *file = iocb->ki_filp;
char *buf = file->private_data;
+ loff_t *fpos = &iocb->ki_pos;
+
size_t phdrs_offset, notes_offset, data_offset;
size_t page_offline_frozen = 1;
size_t phdrs_len, notes_len;
@@ -318,6 +321,7 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
size_t tsz;
int nphdr;
unsigned long start;
+ size_t buflen = iov_iter_count(iter);
size_t orig_buflen = buflen;
int ret = 0;

@@ -356,12 +360,11 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
};

tsz = min_t(size_t, buflen, sizeof(struct elfhdr) - *fpos);
- if (copy_to_user(buffer, (char *)&ehdr + *fpos, tsz)) {
+ if (copy_to_iter((char *)&ehdr + *fpos, tsz, iter) != tsz) {
ret = -EFAULT;
goto out;
}

- buffer += tsz;
buflen -= tsz;
*fpos += tsz;
}
@@ -398,15 +401,14 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
}

tsz = min_t(size_t, buflen, phdrs_offset + phdrs_len - *fpos);
- if (copy_to_user(buffer, (char *)phdrs + *fpos - phdrs_offset,
- tsz)) {
+ if (copy_to_iter((char *)phdrs + *fpos - phdrs_offset, tsz,
+ iter) != tsz) {
kfree(phdrs);
ret = -EFAULT;
goto out;
}
kfree(phdrs);

- buffer += tsz;
buflen -= tsz;
*fpos += tsz;
}
@@ -448,14 +450,13 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
min(vmcoreinfo_size, notes_len - i));

tsz = min_t(size_t, buflen, notes_offset + notes_len - *fpos);
- if (copy_to_user(buffer, notes + *fpos - notes_offset, tsz)) {
+ if (copy_to_iter(notes + *fpos - notes_offset, tsz, iter) != tsz) {
kfree(notes);
ret = -EFAULT;
goto out;
}
kfree(notes);

- buffer += tsz;
buflen -= tsz;
*fpos += tsz;
}
@@ -497,7 +498,7 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
}

if (!m) {
- if (clear_user(buffer, tsz)) {
+ if (iov_iter_zero(tsz, iter) != tsz) {
ret = -EFAULT;
goto out;
}
@@ -508,14 +509,14 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
case KCORE_VMALLOC:
vread(buf, (char *)start, tsz);
/* we have to zero-fill user buffer even if no read */
- if (copy_to_user(buffer, buf, tsz)) {
+ if (copy_to_iter(buf, tsz, iter) != tsz) {
ret = -EFAULT;
goto out;
}
break;
case KCORE_USER:
/* User page is handled prior to normal kernel page: */
- if (copy_to_user(buffer, (char *)start, tsz)) {
+ if (copy_to_iter((char *)start, tsz, iter) != tsz) {
ret = -EFAULT;
goto out;
}
@@ -531,7 +532,7 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
*/
if (!page || PageOffline(page) ||
is_page_hwpoison(page) || !pfn_is_ram(pfn)) {
- if (clear_user(buffer, tsz)) {
+ if (iov_iter_zero(tsz, iter) != tsz) {
ret = -EFAULT;
goto out;
}
@@ -541,17 +542,17 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
case KCORE_VMEMMAP:
case KCORE_TEXT:
/*
- * We use _copy_to_user() to bypass usermode hardening
+ * We use _copy_to_iter() to bypass usermode hardening
* which would otherwise prevent this operation.
*/
- if (_copy_to_user(buffer, (char *)start, tsz)) {
+ if (_copy_to_iter((char *)start, tsz, iter) != tsz) {
ret = -EFAULT;
goto out;
}
break;
default:
pr_warn_once("Unhandled KCORE type: %d\n", m->type);
- if (clear_user(buffer, tsz)) {
+ if (iov_iter_zero(tsz, iter) != tsz) {
ret = -EFAULT;
goto out;
}
@@ -559,7 +560,6 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
skip:
buflen -= tsz;
*fpos += tsz;
- buffer += tsz;
start += tsz;
tsz = (buflen > PAGE_SIZE ? PAGE_SIZE : buflen);
}
@@ -603,7 +603,7 @@ static int release_kcore(struct inode *inode, struct file *file)
}

static const struct proc_ops kcore_proc_ops = {
- .proc_read = read_kcore,
+ .proc_read_iter = read_kcore_iter,
.proc_open = open_kcore,
.proc_release = release_kcore,
.proc_lseek = default_llseek,
--
2.39.2