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authorAl Viro <viro@zeniv.linux.org.uk>2020-01-20 19:49:57 -0500
committerAl Viro <viro@zeniv.linux.org.uk>2020-02-03 21:23:33 -0500
commit12efec5602744c5a185049eb4fcfd9aebe01bd6f (patch)
treec5ce755194abc4b40971b1e235521166f193a24a /fs
parent324282c0252a44a97d628813e30ea7258940d469 (diff)
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saner copy_mount_options()
don't bother with the byte-by-byte loops, etc. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs')
-rw-r--r--fs/namespace.c49
1 files changed, 7 insertions, 42 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index 5e1bf611a9eb..85b5f7bea82e 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2979,39 +2979,10 @@ static void shrink_submounts(struct mount *mnt)
}
}
-/*
- * Some copy_from_user() implementations do not return the exact number of
- * bytes remaining to copy on a fault. But copy_mount_options() requires that.
- * Note that this function differs from copy_from_user() in that it will oops
- * on bad values of `to', rather than returning a short copy.
- */
-static long exact_copy_from_user(void *to, const void __user * from,
- unsigned long n)
-{
- char *t = to;
- const char __user *f = from;
- char c;
-
- if (!access_ok(from, n))
- return n;
-
- while (n) {
- if (__get_user(c, f)) {
- memset(t, 0, n);
- break;
- }
- *t++ = c;
- f++;
- n--;
- }
- return n;
-}
-
void *copy_mount_options(const void __user * data)
{
- int i;
- unsigned long size;
char *copy;
+ unsigned size;
if (!data)
return NULL;
@@ -3020,22 +2991,16 @@ void *copy_mount_options(const void __user * data)
if (!copy)
return ERR_PTR(-ENOMEM);
- /* We only care that *some* data at the address the user
- * gave us is valid. Just in case, we'll zero
- * the remainder of the page.
- */
- /* copy_from_user cannot cross TASK_SIZE ! */
- size = TASK_SIZE - (unsigned long)untagged_addr(data);
- if (size > PAGE_SIZE)
- size = PAGE_SIZE;
+ size = PAGE_SIZE - offset_in_page(data);
- i = size - exact_copy_from_user(copy, data, size);
- if (!i) {
+ if (copy_from_user(copy, data, size)) {
kfree(copy);
return ERR_PTR(-EFAULT);
}
- if (i != PAGE_SIZE)
- memset(copy + i, 0, PAGE_SIZE - i);
+ if (size != PAGE_SIZE) {
+ if (copy_from_user(copy + size, data + size, PAGE_SIZE - size))
+ memset(copy + size, 0, PAGE_SIZE - size);
+ }
return copy;
}