| Message ID | 20180309190736.GA4657@beast (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Mar 9, 2018 at 11:07 AM, Kees Cook <keescook@chromium.org> wrote: > The LSM check should happen after the file has been confirmed to be > unchanging. Without this, we could have a ToCToU issue between the > LSM verification and the actual contents of the file later. Can we please not add random crazy six-letter acronyms that nobody uses outside of a very small community? The point of a commit message is to *explain*, not confuse. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/exec.c b/fs/exec.c index 7eb8d21bcab9..a919a827d181 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -895,13 +895,13 @@ int kernel_read_file(struct file *file, void **buf, loff_t *size, if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0) return -EINVAL; - ret = security_kernel_read_file(file, id); + ret = deny_write_access(file); if (ret) return ret; - ret = deny_write_access(file); + ret = security_kernel_read_file(file, id); if (ret) - return ret; + goto out; i_size = i_size_read(file_inode(file)); if (max_size > 0 && i_size > max_size) {
The LSM check should happen after the file has been confirmed to be unchanging. Without this, we could have a ToCToU issue between the LSM verification and the actual contents of the file later. Signed-off-by: Kees Cook <keescook@chromium.org> --- Only loadpin and SELinux implement this hook. From what I can see, this won't change anything for either of them. IMA calls kernel_read_file(), but looking there it seems those callers won't be negatively impacted either. Can folks double-check this and send an Ack please? --- fs/exec.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)