From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> BugLink: https://bugs.launchpad.net/bugs/1950644 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> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> (cherry picked from commit 032146cda85566abcd1c4884d9d23e4e30a07e9a) Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxxxxx> --- 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 90d255fbdd9b..c84d87f558cb 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); -- 2.32.0
