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.

Reported-by: Hao Sun sunhao.th@gmail.com Fixes: b844f0ecbc56 ("vfs: define kernel_copy_file_from_fd()") Cc: stable@vger.kernel.org Signed-off-by: Matthew Wilcox (Oracle) willy@infradead.org --- fs/kernel_read_file.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/kernel_read_file.c b/fs/kernel_read_file.c index 87aac4c72c37..1b07550485b9 100644 --- a/fs/kernel_read_file.c +++ b/fs/kernel_read_file.c @@ -178,7 +178,7 @@ int kernel_read_file_from_fd(int fd, loff_t offset, void **buf, 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, offset, buf, buf_size, file_size, id);