+ lib-free-pagelist-on-error-in-iov_iter_extract_pages.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: lib: free pagelist on error in iov_iter_extract_pages()
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     lib-free-pagelist-on-error-in-iov_iter_extract_pages.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/lib-free-pagelist-on-error-in-iov_iter_extract_pages.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days

------------------------------------------------------
From: Dmitry Antipov <dmantipov@yandex.ru>
Subject: lib: free pagelist on error in iov_iter_extract_pages()
Date: Fri, 8 May 2026 14:13:29 +0300

Since 'iov_iter_extract_pages()' may allocate new pagelist if the passed
one isn't large enough, the worst-case scenario may be:

...
struct page *stack_pages[SMALL];
struct page **pages = stack_pages;
...
if (iov_iter_extract_pages(i..., &pages, ...) <= 0) {
        /* Even in case of error, new pagelist may be allocated */
        if (pages != stack_pages)
                kvfree(pages);                                  [1]
        /* The rest of error handling and return */
}
/* Regular flow */
...
if (pages != stack_pages)
        kvfree(pages);
...
return 0;

If you're unlucky so SMALL amount of pages wasn't enough and new pagelist
was allocated, missing [1] causes the memory leak similar to one I've
recently observed and fixed for 6.12 in [2].  So adjust
'iov_iter_extract_pages()' to make such a cleanup itself rather than rely
on caller's handling on error paths, thus making [1] not needed.

[2] https://lore.kernel.org/stable/20260505094529.406783-1-dmantipov@yandex.ru/T/#u

Link: https://lore.kernel.org/20260508111329.329943-1-dmantipov@yandex.ru
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Suggested-by: Fedor Pchelkin <pchelkin@ispras.ru>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 lib/iov_iter.c |   54 ++++++++++++++++++++++++++++-------------------
 1 file changed, 33 insertions(+), 21 deletions(-)

--- a/lib/iov_iter.c~lib-free-pagelist-on-error-in-iov_iter_extract_pages
+++ a/lib/iov_iter.c
@@ -1807,7 +1807,8 @@ static ssize_t iov_iter_extract_user_pag
  *  (*) Use with ITER_DISCARD is not supported as that has no content.
  *
  * On success, the function sets *@pages to the new pagelist, if allocated, and
- * sets *offset0 to the offset into the first page.
+ * sets *offset0 to the offset into the first page. On error, new pagelist
+ * is freed if was allocated, and *@pages sets back to its original value.
  *
  * It may also return -ENOMEM and -EFAULT.
  */
@@ -1818,31 +1819,42 @@ ssize_t iov_iter_extract_pages(struct io
 			       iov_iter_extraction_t extraction_flags,
 			       size_t *offset0)
 {
+	struct page **oldpages = *pages;
+	int ret;
+
 	maxsize = min_t(size_t, min_t(size_t, maxsize, i->count), MAX_RW_COUNT);
 	if (!maxsize)
 		return 0;
 
 	if (likely(user_backed_iter(i)))
-		return iov_iter_extract_user_pages(i, pages, maxsize,
-						   maxpages, extraction_flags,
-						   offset0);
-	if (iov_iter_is_kvec(i))
-		return iov_iter_extract_kvec_pages(i, pages, maxsize,
-						   maxpages, extraction_flags,
-						   offset0);
-	if (iov_iter_is_bvec(i))
-		return iov_iter_extract_bvec_pages(i, pages, maxsize,
-						   maxpages, extraction_flags,
-						   offset0);
-	if (iov_iter_is_folioq(i))
-		return iov_iter_extract_folioq_pages(i, pages, maxsize,
-						     maxpages, extraction_flags,
-						     offset0);
-	if (iov_iter_is_xarray(i))
-		return iov_iter_extract_xarray_pages(i, pages, maxsize,
-						     maxpages, extraction_flags,
-						     offset0);
-	return -EFAULT;
+		ret = iov_iter_extract_user_pages(i, pages, maxsize,
+						  maxpages, extraction_flags,
+						  offset0);
+	else if (iov_iter_is_kvec(i))
+		ret = iov_iter_extract_kvec_pages(i, pages, maxsize,
+						  maxpages, extraction_flags,
+						  offset0);
+	else if (iov_iter_is_bvec(i))
+		ret = iov_iter_extract_bvec_pages(i, pages, maxsize,
+						  maxpages, extraction_flags,
+						  offset0);
+	else if (iov_iter_is_folioq(i))
+		ret = iov_iter_extract_folioq_pages(i, pages, maxsize,
+						    maxpages, extraction_flags,
+						    offset0);
+	else if (iov_iter_is_xarray(i))
+		ret = iov_iter_extract_xarray_pages(i, pages, maxsize,
+						    maxpages, extraction_flags,
+						    offset0);
+	else
+		ret = -EFAULT;
+
+	if (unlikely(ret) && *pages && *pages != oldpages) {
+		kvfree(*pages);
+		*pages = oldpages;
+	}
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(iov_iter_extract_pages);
 
_

Patches currently in -mm which might be from dmantipov@yandex.ru are

lib-free-pagelist-on-error-in-iov_iter_extract_pages.patch
lib-fix-_parse_integer_limit-to-handle-overflow.patch
lib-fix-memparse-to-handle-overflow.patch
lib-add-more-string-to-64-bit-integer-conversion-overflow-tests.patch
lib-cmdline_kunit-add-test-case-for-memparse.patch
lib-cmdline-adjust-a-few-comments-to-fix-kernel-doc-wreturn-warnings.patch
riscv-export-symbols-needed-for-riscv32-efi-stub.patch