compat breakage in preadv() and pwritev()

PATCH New Al Viro 1 participant 1 message Mar 13, 2011 VFS

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Al Viro

author maintainer

2011-03-13 23:24 UTC #0 lore raw

PATCH 1/1 compat breakage in preadv() and pwritev()

Fix for a dumb preadv()/pwritev() compat bug - unlike the native
variants, 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 <[email protected]>

---
 fs/compat.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

fs/compat.c +6 -2

index f6fd0a0..691c3fd 100644
@@ -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;
 }