From 6e7ca99d18d0b57aecbd760a422ab42ea256f634 Mon Sep 17 00:00:00 2001 From: Andrew Morton Date: Thu, 26 Aug 2004 20:34:16 -0700 Subject: [PATCH] [PATCH] copy_mount_options size fix davem says that copy_mount_options is failing in obscure ways if the architecture's copy_from_user() doesn't return an exact count of the number of uncopied bytes. Fixing that up in each architecture is a pain - it involves falling back to byte-at-a-time copies. It's simple to open-code this in namespace.c. If we find other places in the kernel which care about this we can promote this to a global function. Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/namespace.c | 32 ++++++++++++++++++++++++++++++-- 1 file changed, 30 insertions(+), 2 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 9e8350d458f25..2c5cc697a18db 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -930,7 +930,35 @@ void mark_mounts_for_expiry(struct list_head *mounts) EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); -int copy_mount_options (const void __user *data, unsigned long *where) +/* + * 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(VERIFY_READ, from, n)) + return n; + + while (n) { + if (__get_user(c, f)) { + memset(t, 0, n); + break; + } + *t++ = c; + f++; + n--; + } + return n; +} + +int copy_mount_options(const void __user *data, unsigned long *where) { int i; unsigned long page; @@ -952,7 +980,7 @@ int copy_mount_options (const void __user *data, unsigned long *where) if (size > PAGE_SIZE) size = PAGE_SIZE; - i = size - copy_from_user((void *)page, data, size); + i = size - exact_copy_from_user((void *)page, data, size); if (!i) { free_page(page); return -EFAULT; -- 2.53.0