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From: Eugene Syromiatnikov <esyr@redhat.com>
To: linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Jens Axboe <axboe@kernel.dk>
Cc: linux-kernel@vger.kernel.org, Jeff Moyer <jmoyer@redhat.com>,
	"Dmitry V. Levin" <ldv@altlinux.org>
Subject: [PATCH] io_uring: fix compat for IORING_REGISTER_FILES_UPDATE
Date: Wed, 15 Jan 2020 17:35:38 +0100
Message-ID: <20200115163538.GA13732@asgard.redhat.com> (raw)

fds field of struct io_uring_files_update is problematic with regards
to compat user space, as pointer size is different in 32-bit, 32-on-64-bit,
and 64-bit user space.  In order to avoid custom handling of compat in
the syscall implementation, make fds __u64 and use u64_to_user_ptr in
order to retrieve it.  Also, align the field naturally and check that
no garbage is passed there.

Fixes: c3a31e605620c279 ("io_uring: add support for IORING_REGISTER_FILES_UPDATE")
Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>
---
 fs/io_uring.c                 | 4 +++-
 include/uapi/linux/io_uring.h | 3 ++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 38b5405..677ef90 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4445,13 +4445,15 @@ static int io_sqe_files_update(struct io_ring_ctx *ctx, void __user *arg,
 		return -EINVAL;
 	if (copy_from_user(&up, arg, sizeof(up)))
 		return -EFAULT;
+	if (up.resv)
+		return -EINVAL;
 	if (check_add_overflow(up.offset, nr_args, &done))
 		return -EOVERFLOW;
 	if (done > ctx->nr_user_files)
 		return -EINVAL;
 
 	done = 0;
-	fds = (__s32 __user *) up.fds;
+	fds = u64_to_user_ptr(up.fds);
 	while (nr_args) {
 		struct fixed_file_table *table;
 		unsigned index;
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index a3300e1..55cfcb7 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -178,7 +178,8 @@ struct io_uring_params {
 
 struct io_uring_files_update {
 	__u32 offset;
-	__s32 *fds;
+	__u32 resv;
+	__aligned_u64 /* __s32 * */ fds;
 };
 
 #endif
-- 
2.1.4


             reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-15 16:35 Eugene Syromiatnikov [this message]
2020-01-15 16:41 ` Jens Axboe
2020-01-15 16:50   ` Eugene Syromiatnikov
2020-01-15 16:53     ` Jens Axboe
2020-01-15 16:59       ` Eugene Syromiatnikov

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