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Thu, 22 Aug 2024 10:40:32 +0800 (CST) From: libaokun@huaweicloud.com To: linux-ext4@vger.kernel.org Cc: tytso@mit.edu, adilger.kernel@dilger.ca, jack@suse.cz, ritesh.list@gmail.com, ojaswin@linux.ibm.com, linux-kernel@vger.kernel.org, yi.zhang@huawei.com, yangerkun@huawei.com, libaokun@huaweicloud.com, Baokun Li , stable@kernel.org Subject: [PATCH v2 03/25] ext4: fix slab-use-after-free in ext4_split_extent_at() Date: Thu, 22 Aug 2024 10:35:23 +0800 Message-Id: <20240822023545.1994557-4-libaokun@huaweicloud.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240822023545.1994557-1-libaokun@huaweicloud.com> References: <20240822023545.1994557-1-libaokun@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-CM-TRANSID: gCh0CgCHr4UapcZmqbd1CQ--.38129S7 X-Coremail-Antispam: 1UD129KBjvJXoWxZFyftr13Zr47Ary3Gw48WFg_yoWrWw18pr ykCryxGr15t34DWrZrJF1DZr1xKa1UGw4UJrWfGr12gFyUt348WFyIyF15tF98KrW8Za45 ZF48tryUW3WqkFDanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUmK14x267AKxVWrJVCq3wAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2048vs2IY020E87I2jVAFwI0_JrWl82xGYIkIc2 x26xkF7I0E14v26ryj6s0DM28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48ve4kI8wA2z4x0 Y4vE2Ix0cI8IcVAFwI0_Ar0_tr1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI0_Gr1j6F4UJw A2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AKxVW0oVCq3wAS 0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7IYx2 IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4UM4x0 Y48IcxkI7VAKI48JM4x0x7Aq67IIx4CEVc8vx2IErcIFxwACI402YVCY1x02628vn2kIc2 xKxwAKzVCY07xG64k0F24lc7CjxVAaw2AFwI0_Jw0_GFyl42xK82IYc2Ij64vIr41l4I8I 3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s026x8GjcxK67AKxV WUGVWUWwC2zVAF1VAY17CE14v26r1q6r43MIIYrxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAF wI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I0E14v26r4j6F4UMIIF0xvE42xK8VAvwI8IcI k0rVWUJVWUCwCI42IY6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r4j 6r4UJbIYCTnIWIevJa73UjIFyTuYvjfUOnmRUUUUU X-CM-SenderInfo: 5olet0hnxqqx5xdzvxpfor3voofrz/1tbiAgADBWbFpZhEEgABsN From: Baokun Li We hit the following use-after-free: ================================================================== BUG: KASAN: slab-use-after-free in ext4_split_extent_at+0xba8/0xcc0 Read of size 2 at addr ffff88810548ed08 by task kworker/u20:0/40 CPU: 0 PID: 40 Comm: kworker/u20:0 Not tainted 6.9.0-dirty #724 Call Trace: kasan_report+0x93/0xc0 ext4_split_extent_at+0xba8/0xcc0 ext4_split_extent.isra.0+0x18f/0x500 ext4_split_convert_extents+0x275/0x750 ext4_ext_handle_unwritten_extents+0x73e/0x1580 ext4_ext_map_blocks+0xe20/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] Allocated by task 40: __kmalloc_noprof+0x1ac/0x480 ext4_find_extent+0xf3b/0x1e70 ext4_ext_map_blocks+0x188/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] Freed by task 40: kfree+0xf1/0x2b0 ext4_find_extent+0xa71/0x1e70 ext4_ext_insert_extent+0xa22/0x3260 ext4_split_extent_at+0x3ef/0xcc0 ext4_split_extent.isra.0+0x18f/0x500 ext4_split_convert_extents+0x275/0x750 ext4_ext_handle_unwritten_extents+0x73e/0x1580 ext4_ext_map_blocks+0xe20/0x2dc0 ext4_map_blocks+0x724/0x1700 ext4_do_writepages+0x12d6/0x2a70 [...] ================================================================== The flow of issue triggering is as follows: ext4_split_extent_at path = *ppath ext4_ext_insert_extent(ppath) ext4_ext_create_new_leaf(ppath) ext4_find_extent(orig_path) path = *orig_path read_extent_tree_block // return -ENOMEM or -EIO ext4_free_ext_path(path) kfree(path) *orig_path = NULL a. If err is -ENOMEM: ext4_ext_dirty(path + path->p_depth) // path use-after-free !!! b. If err is -EIO and we have EXT_DEBUG defined: ext4_ext_show_leaf(path) eh = path[depth].p_hdr // path also use-after-free !!! So when trying to zeroout or fix the extent length, call ext4_find_extent() to update the path. In addition we use *ppath directly as an ext4_ext_show_leaf() input to avoid possible use-after-free when EXT_DEBUG is defined, and to avoid unnecessary path updates. Fixes: dfe5080939ea ("ext4: drop EXT4_EX_NOFREE_ON_ERR from rest of extents handling code") Cc: stable@kernel.org Signed-off-by: Baokun Li Reviewed-by: Jan Kara Reviewed-by: Ojaswin Mujoo Tested-by: Ojaswin Mujoo --- fs/ext4/extents.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 4d589d34b30e..ff4cfd8edeb7 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -3251,6 +3251,25 @@ static int ext4_split_extent_at(handle_t *handle, if (err != -ENOSPC && err != -EDQUOT && err != -ENOMEM) goto out; + /* + * Update path is required because previous ext4_ext_insert_extent() + * may have freed or reallocated the path. Using EXT4_EX_NOFAIL + * guarantees that ext4_find_extent() will not return -ENOMEM, + * otherwise -ENOMEM will cause a retry in do_writepages(), and a + * WARN_ON may be triggered in ext4_da_update_reserve_space() due to + * an incorrect ee_len causing the i_reserved_data_blocks exception. + */ + path = ext4_find_extent(inode, ee_block, ppath, + flags | EXT4_EX_NOFAIL); + if (IS_ERR(path)) { + EXT4_ERROR_INODE(inode, "Failed split extent on %u, err %ld", + split, PTR_ERR(path)); + return PTR_ERR(path); + } + depth = ext_depth(inode); + ex = path[depth].p_ext; + *ppath = path; + if (EXT4_EXT_MAY_ZEROOUT & split_flag) { if (split_flag & (EXT4_EXT_DATA_VALID1|EXT4_EXT_DATA_VALID2)) { if (split_flag & EXT4_EXT_DATA_VALID1) { @@ -3303,7 +3322,7 @@ static int ext4_split_extent_at(handle_t *handle, ext4_ext_dirty(handle, inode, path + path->p_depth); return err; out: - ext4_ext_show_leaf(inode, path); + ext4_ext_show_leaf(inode, *ppath); return err; }