path: root/fs/open.c
diff options
authorKees Cook <>2020-08-11 18:36:26 -0700
committerLinus Torvalds <>2020-08-12 10:58:01 -0700
commit633fb6ac39801514613fbe050db6abdc3fe744d5 (patch)
treeb2a4509122ee07078297aa873319c1e2473de379 /fs/open.c
parentdb19c91c3b75cf8ece3ffd92a4e84a306a7547b0 (diff)
exec: move S_ISREG() check earlier
The execve(2)/uselib(2) syscalls have always rejected non-regular files. Recently, it was noticed that a deadlock was introduced when trying to execute pipes, as the S_ISREG() test was happening too late. This was fixed in commit 73601ea5b7b1 ("fs/open.c: allow opening only regular files during execve()"), but it was added after inode_permission() had already run, which meant LSMs could see bogus attempts to execute non-regular files. Move the test into the other inode type checks (which already look for other pathological conditions[1]). Since there is no need to use FMODE_EXEC while we still have access to "acc_mode", also switch the test to MAY_EXEC. Also include a comment with the redundant S_ISREG() checks at the end of execve(2)/uselib(2) to note that they are present to avoid any mistakes. My notes on the call path, and related arguments, checks, etc: do_open_execat() struct open_flags open_exec_flags = { .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC, .acc_mode = MAY_EXEC, ... do_filp_open(dfd, filename, open_flags) path_openat(nameidata, open_flags, flags) file = alloc_empty_file(open_flags, current_cred()); do_open(nameidata, file, open_flags) may_open(path, acc_mode, open_flag) /* new location of MAY_EXEC vs S_ISREG() test */ inode_permission(inode, MAY_OPEN | acc_mode) security_inode_permission(inode, acc_mode) vfs_open(path, file) do_dentry_open(file, path->dentry->d_inode, open) /* old location of FMODE_EXEC vs S_ISREG() test */ security_file_open(f) open() [1] Signed-off-by: Kees Cook <> Signed-off-by: Andrew Morton <> Cc: Aleksa Sarai <> Cc: Alexander Viro <> Cc: Christian Brauner <> Cc: Dmitry Vyukov <> Cc: Eric Biggers <> Cc: Tetsuo Handa <> Link: Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'fs/open.c')
1 files changed, 0 insertions, 6 deletions
diff --git a/fs/open.c b/fs/open.c
index c80e9f497e9b..9af548fb841b 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -779,12 +779,6 @@ static int do_dentry_open(struct file *f,
return 0;
- /* Any file opened for execve()/uselib() has to be a regular file. */
- if (unlikely(f->f_flags & FMODE_EXEC && !S_ISREG(inode->i_mode))) {
- error = -EACCES;
- goto cleanup_file;
- }
if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
error = get_write_access(inode);
if (unlikely(error))