linux-kernel - [PATCH v2] vfs: fix find_lock_page

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 3 Apr 2009 16:35:59 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Ying Han <yinghan@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, mingo@...e.hu, mikew@...gle.com,
	rientjes@...gle.com, rohitseth@...gle.com, hugh@...itas.com,
	a.p.zijlstra@...llo.nl, hpa@...or.com, edwintorok@...il.com,
	lee.schermerhorn@...com, npiggin@...e.de
Subject: [PATCH v2] vfs: fix find_lock_page_retry() return value parsing

find_lock_page_retry() won't touch the *ppage value when returning
VM_FAULT_RETRY. This is fine except for the case

        if (VM_RandomReadHint())
                goto no_cached_page;

where the 'page' could be undefined after calling find_lock_page_retry().

Fix it by checking the VM_FAULT_RETRY case first. Also do this for the
other two find_lock_page_retry() invocations for the sake of consistency.

Cc: Ying Han <yinghan@...gle.com>
Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
---
 mm/filemap.c |   14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

--- mm.orig/mm/filemap.c
+++ mm/mm/filemap.c
@@ -759,7 +759,7 @@ EXPORT_SYMBOL(find_lock_page);
  * @retry: 1 indicate caller tolerate a retry.
  *
  * If retry flag is on, and page is already locked by someone else, return
- * a hint of retry.
+ * a hint of retry and leave *ppage untouched.
  *
  * Return *ppage==NULL if page is not in pagecache. Otherwise return *ppage
  * points to the page in the pagecache with ret=VM_FAULT_RETRY indicate a
@@ -1575,10 +1575,10 @@ retry_find_nopage:
 							   vmf->pgoff, 1);
 			retry_ret = find_lock_page_retry(mapping, vmf->pgoff,
 						vma, &page, retry_flag);
-			if (!page)
-				goto no_cached_page;
 			if (retry_ret == VM_FAULT_RETRY)
 				return retry_ret;
+			if (!page)
+				goto no_cached_page;
 		}
 		if (PageReadahead(page)) {
 			page_cache_async_readahead(mapping, ra, file, page,
@@ -1617,10 +1617,10 @@ retry_find_nopage:
 		}
 		retry_ret = find_lock_page_retry(mapping, vmf->pgoff,
 				vma, &page, retry_flag);
-		if (!page)
-			goto no_cached_page;
 		if (retry_ret == VM_FAULT_RETRY)
 			return retry_ret;
+		if (!page)
+			goto no_cached_page;
 	}
 
 	if (!did_readaround)
@@ -1672,10 +1672,10 @@ no_cached_page:
 
 		retry_ret = find_lock_page_retry(mapping, vmf->pgoff,
 					vma, &page, retry_flag);
+		if (retry_ret == VM_FAULT_RETRY)
+			return retry_ret;
 		if (!page)
 			goto retry_find_nopage;
-		else if (retry_ret == VM_FAULT_RETRY)
-			return retry_ret;
 		else
 			goto retry_page_update;
 	}
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/