From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Subject: vfs: check fd has read access in kernel_read_file_from_fd()
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@xxxxxxxxxxxxx
Fixes: b844f0ecbc56 ("vfs: define kernel_copy_file_from_fd()")
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reported-by: Hao Sun <sunhao.th@xxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Acked-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Mimi Zohar <zohar@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/kernel_read_file.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/kernel_read_file.c~vfs-check-fd-has-read-access-in-kernel_read_file_from_fd
+++ a/fs/kernel_read_file.c
@@ -178,7 +178,7 @@ int kernel_read_file_from_fd(int fd, lof
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);
_
