From: "Matthew Wilcox (Oracle)" <willy@infradead.org> stable inclusion from linux-4.19.214 commit c1ba20965b59c2eeb54a845ca5cab4fc7bcf9735 -------------------------------- commit 032146cda85566abcd1c4884d9d23e4e30a07e9a upstream. If we open a file without read access and then pass the fd to a syscall whose implementation calls kernel_read_file_from_fd(), we get a warning from __kernel_read(): if (WARN_ON_ONCE(!(file->f_mode & FMODE_READ))) This currently affects both finit_module() and kexec_file_load(), but it could affect other syscalls in the future. Link: https://lkml.kernel.org/r/20211007220110.600005-1-willy@infradead.org Fixes: b844f0ecbc56 ("vfs: define kernel_copy_file_from_fd()") Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Reported-by: Hao Sun <sunhao.th@gmail.com> Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Christian Brauner <christian.brauner@ubuntu.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Mimi Zohar <zohar@linux.ibm.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: Jason Yan <yanaijie@huawei.com> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- fs/exec.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/exec.c b/fs/exec.c index 07b536eb6c446..426842c38ecb6 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -984,7 +984,7 @@ int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size, struct fd f = fdget(fd); int ret = -EBADF; - if (!f.file) + if (!f.file || !(f.file->f_mode & FMODE_READ)) goto out; ret = kernel_read_file(f.file, buf, size, max_size, id); -- 2.25.1