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[68.40.189.247]) by smtp.gmail.com with ESMTPSA id u136sm7185529ywf.101.2020.02.02.14.56.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 02 Feb 2020 14:56:08 -0800 (PST) From: Trond Myklebust X-Google-Original-From: Trond Myklebust To: Anna Schumaker Cc: Benjamin Coddington , Dai Ngo , linux-nfs@vger.kernel.org Subject: [PATCH 2/4] NFS: Directory page cache pages need to be locked when read Date: Sun, 2 Feb 2020 17:53:54 -0500 Message-Id: <20200202225356.995080-3-trond.myklebust@hammerspace.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200202225356.995080-2-trond.myklebust@hammerspace.com> References: <20200202225356.995080-1-trond.myklebust@hammerspace.com> <20200202225356.995080-2-trond.myklebust@hammerspace.com> MIME-Version: 1.0 Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org When a NFS directory page cache page is removed from the page cache, its contents are freed through a call to nfs_readdir_clear_array(). To prevent the removal of the page cache entry until after we've finished reading it, we must take the page lock. Fixes: 11de3b11e08c ("NFS: Fix a memory leak in nfs_readdir") Cc: stable@vger.kernel.org # v2.6.37+ Signed-off-by: Trond Myklebust Reviewed-by: Benjamin Coddington --- fs/nfs/dir.c | 30 +++++++++++++++++++----------- 1 file changed, 19 insertions(+), 11 deletions(-) diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index ba0d55930e8a..90467b44ec13 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -705,8 +705,6 @@ int nfs_readdir_filler(void *data, struct page* page) static void cache_page_release(nfs_readdir_descriptor_t *desc) { - if (!desc->page->mapping) - nfs_readdir_clear_array(desc->page); put_page(desc->page); desc->page = NULL; } @@ -720,19 +718,28 @@ struct page *get_cache_page(nfs_readdir_descriptor_t *desc) /* * Returns 0 if desc->dir_cookie was found on page desc->page_index + * and locks the page to prevent removal from the page cache. */ static -int find_cache_page(nfs_readdir_descriptor_t *desc) +int find_and_lock_cache_page(nfs_readdir_descriptor_t *desc) { int res; desc->page = get_cache_page(desc); if (IS_ERR(desc->page)) return PTR_ERR(desc->page); - - res = nfs_readdir_search_array(desc); + res = lock_page_killable(desc->page); if (res != 0) - cache_page_release(desc); + goto error; + res = -EAGAIN; + if (desc->page->mapping != NULL) { + res = nfs_readdir_search_array(desc); + if (res == 0) + return 0; + } + unlock_page(desc->page); +error: + cache_page_release(desc); return res; } @@ -747,7 +754,7 @@ int readdir_search_pagecache(nfs_readdir_descriptor_t *desc) desc->last_cookie = 0; } do { - res = find_cache_page(desc); + res = find_and_lock_cache_page(desc); } while (res == -EAGAIN); return res; } @@ -786,7 +793,6 @@ int nfs_do_filldir(nfs_readdir_descriptor_t *desc) desc->eof = true; kunmap(desc->page); - cache_page_release(desc); dfprintk(DIRCACHE, "NFS: nfs_do_filldir() filling ended @ cookie %Lu; returning = %d\n", (unsigned long long)*desc->dir_cookie, res); return res; @@ -832,13 +838,13 @@ int uncached_readdir(nfs_readdir_descriptor_t *desc) status = nfs_do_filldir(desc); + out_release: + nfs_readdir_clear_array(desc->page); + cache_page_release(desc); out: dfprintk(DIRCACHE, "NFS: %s: returns %d\n", __func__, status); return status; - out_release: - cache_page_release(desc); - goto out; } /* The file offset position represents the dirent entry number. A @@ -903,6 +909,8 @@ static int nfs_readdir(struct file *file, struct dir_context *ctx) break; res = nfs_do_filldir(desc); + unlock_page(desc->page); + cache_page_release(desc); if (res < 0) break; } while (!desc->eof);