On 2020-06-05 22:19, a...@linux-foundation.org wrote:
The patch titled
Subject: exec: open code copy_string_kernel
has been removed from the -mm tree. Its filename was
exec-open-code-copy_string_kernel.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Christoph Hellwig <h...@lst.de>
Subject: exec: open code copy_string_kernel
Currently copy_string_kernel is just a wrapper around copy_strings that
simplifies the calling conventions and uses set_fs to allow passing a
kernel pointer. But due to the fact the we only need to handle a single
kernel argument pointer, the logic can be sigificantly simplified while
getting rid of the set_fs.
Link: http://lkml.kernel.org/r/20200501104105.2621149-3-...@lst.de
Signed-off-by: Christoph Hellwig <h...@lst.de>
Cc: Alexander Viro <v...@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
---
fs/exec.c | 45 +++++++++++++++++++++++++++++++++++----------
1 file changed, 35 insertions(+), 10 deletions(-)
--- a/fs/exec.c~exec-open-code-copy_string_kernel
+++ a/fs/exec.c
@@ -592,17 +592,42 @@ out:
*/
int copy_string_kernel(const char *arg, struct linux_binprm *bprm)
{
- int r;
- mm_segment_t oldfs = get_fs();
- struct user_arg_ptr argv = {
- .ptr.native = (const char __user *const __user *)&arg,
- };
-
- set_fs(KERNEL_DS);
- r = copy_strings(1, argv, bprm);
- set_fs(oldfs);
+ int len = strnlen(arg, MAX_ARG_STRLEN) + 1 /* terminating NUL */;
+ unsigned long pos = bprm->p;
- return r;
+ if (len == 0)
+ return -EFAULT;
Just a quick question, how can len ever be 0 here when len was set to
strnlen() + 1? Should the test be different?
The old version (i.e. copy_strings()) seems to return -EFAULT when
strnlen() returns 0.
Vegard
+ if (!valid_arg_len(bprm, len))
+ return -E2BIG;
+
+ /* We're going to work our way backwards. */
+ arg += len;
+ bprm->p -= len;
+ if (IS_ENABLED(CONFIG_MMU) && bprm->p < bprm->argmin)
+ return -E2BIG;
+
+ while (len > 0) {
+ unsigned int bytes_to_copy = min_t(unsigned int, len,
+ min_not_zero(offset_in_page(pos), PAGE_SIZE));
+ struct page *page;
+ char *kaddr;
+
+ pos -= bytes_to_copy;
+ arg -= bytes_to_copy;
+ len -= bytes_to_copy;
+
+ page = get_arg_page(bprm, pos, 1);
+ if (!page)
+ return -E2BIG;
+ kaddr = kmap_atomic(page);
+ flush_arg_page(bprm, pos & PAGE_MASK, page);
+ memcpy(kaddr + offset_in_page(pos), arg, bytes_to_copy);
+ flush_kernel_dcache_page(page);
+ kunmap_atomic(kaddr);
+ put_arg_page(page);
+ }
+
+ return 0;
}
EXPORT_SYMBOL(copy_string_kernel);
