From f11b55d13563e9428c88c873f4f03a6bef11ec0a Mon Sep 17 00:00:00 2001 From: Dmitry Monakhov Date: Fri, 31 Mar 2017 19:53:35 +0400 Subject: [PATCH] tcm_fileio: Prevent information leak for short reads If we failed to read data from backing file (probably because some one truncate file under us), we must zerofill cmd's data, otherwise it will be returned as is. Most likely cmd's data are unitialized pages from page cache. This result in information leak. (Change BUG_ON into -EINVAL se_cmd failure - nab) testcase: https://github.com/dmonakhov/xfstests/commit/e11a1b7b907ca67b1be51a1594025600767366d5 Signed-off-by: Dmitry Monakhov Signed-off-by: Nicholas Bellinger --- drivers/target/target_core_file.c | 23 +++++++++++++++++------ 1 file changed, 17 insertions(+), 6 deletions(-) diff --git a/drivers/target/target_core_file.c b/drivers/target/target_core_file.c index 87aa376a1a1a..dd8f32055266 100644 --- a/drivers/target/target_core_file.c +++ b/drivers/target/target_core_file.c @@ -277,12 +277,11 @@ static int fd_do_rw(struct se_cmd *cmd, struct file *fd, else ret = vfs_iter_read(fd, &iter, &pos); - kfree(bvec); - if (is_write) { if (ret < 0 || ret != data_length) { pr_err("%s() write returned %d\n", __func__, ret); - return (ret < 0 ? ret : -EINVAL); + if (ret >= 0) + ret = -EINVAL; } } else { /* @@ -295,17 +294,29 @@ static int fd_do_rw(struct se_cmd *cmd, struct file *fd, pr_err("%s() returned %d, expecting %u for " "S_ISBLK\n", __func__, ret, data_length); - return (ret < 0 ? ret : -EINVAL); + if (ret >= 0) + ret = -EINVAL; } } else { if (ret < 0) { pr_err("%s() returned %d for non S_ISBLK\n", __func__, ret); - return ret; + } else if (ret != data_length) { + /* + * Short read case: + * Probably some one truncate file under us. + * We must explicitly zero sg-pages to prevent + * expose uninizialized pages to userspace. + */ + if (ret < data_length) + ret += iov_iter_zero(data_length - ret, &iter); + else + ret = -EINVAL; } } } - return 1; + kfree(bvec); + return ret; } static sense_reason_t -- 2.20.1