compat breakage in preadv() and pwritev()

Fix for a dumb preadv()/pwritev() compat bug - unlike the native
variants, the compat_...  ones forget to check FMODE_P{READ,WRITE}, so
e.g.  on pipe the native preadv() will fail with -ESPIPE and compat one
will act as readv() and succeed.

Not critical, but it's a clear bug with trivial fix, so IMO it's OK for
-final.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/compat.c b/fs/compat.c
index f6fd0a0..691c3fd 100644 (file)
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -1228,7 +1228,9 @@ compat_sys_preadv(unsigned long fd, const struct compat_iovec __user *vec,
        file = fget_light(fd, &fput_needed);
        if (!file)
                return -EBADF;
-       ret = compat_readv(file, vec, vlen, &pos);
+       ret = -ESPIPE;
+       if (file->f_mode & FMODE_PREAD)
+               ret = compat_readv(file, vec, vlen, &pos);
        fput_light(file, fput_needed);
        return ret;
 }
@@ -1285,7 +1287,9 @@ compat_sys_pwritev(unsigned long fd, const struct compat_iovec __user *vec,
        file = fget_light(fd, &fput_needed);
        if (!file)
                return -EBADF;
-       ret = compat_writev(file, vec, vlen, &pos);
+       ret = -ESPIPE;
+       if (file->f_mode & FMODE_PWRITE)
+               ret = compat_writev(file, vec, vlen, &pos);
        fput_light(file, fput_needed);
        return ret;
 }