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From: Leon Romanovsky <leonro@mellanox.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: linux-rdma@vger.kernel.org,
	syzbot+086ab5ca9eafd2379aa6@syzkaller.appspotmail.com,
	syzbot+7446526858b83c8828b2@syzkaller.appspotmail.com
Subject: Re: [PATCH] RDMA/cm: Add min length checks to user structure copies
Date: Fri, 24 Jul 2020 16:45:45 +0300
Message-ID: <20200724134545.GB5479@unreal> (raw)
In-Reply-To: <0-v1-d5b86dab17dc+28c25-ucma_syz_min_jgg@nvidia.com>

On Fri, Jul 24, 2020 at 10:19:29AM -0300, Jason Gunthorpe wrote:
> These are missing throughout ucma, it harmlessly copies garbage from
> userspace, but in this new code which uses min to compute the copy length
> it can result in uninitialized stack memory. Check for minimum length at
> the very start.
>
>   BUG: KMSAN: uninit-value in ucma_connect+0x2aa/0xab0 drivers/infiniband/core/ucma.c:1091
>   CPU: 0 PID: 8457 Comm: syz-executor069 Not tainted 5.8.0-rc5-syzkaller #0
>   Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
>   Call Trace:
>    __dump_stack lib/dump_stack.c:77 [inline]
>    dump_stack+0x1df/0x240 lib/dump_stack.c:118
>    kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:121
>    __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215
>    ucma_connect+0x2aa/0xab0 drivers/infiniband/core/ucma.c:1091
>    ucma_write+0x5c5/0x630 drivers/infiniband/core/ucma.c:1764
>    do_loop_readv_writev fs/read_write.c:737 [inline]
>    do_iter_write+0x710/0xdc0 fs/read_write.c:1020
>    vfs_writev fs/read_write.c:1091 [inline]
>    do_writev+0x42d/0x8f0 fs/read_write.c:1134
>    __do_sys_writev fs/read_write.c:1207 [inline]
>    __se_sys_writev+0x9b/0xb0 fs/read_write.c:1204
>    __x64_sys_writev+0x4a/0x70 fs/read_write.c:1204
>    do_syscall_64+0xb0/0x150 arch/x86/entry/common.c:386
>    entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> Fixes: 34e2ab57a911 ("RDMA/ucma: Extend ucma_connect to receive ECE parameters")
> Fixes: 0cb15372a615 ("RDMA/cma: Connect ECE to rdma_accept")
> Reported-by: syzbot+086ab5ca9eafd2379aa6@syzkaller.appspotmail.com
> Reported-by: syzbot+7446526858b83c8828b2@syzkaller.appspotmail.com
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>  drivers/infiniband/core/ucma.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/infiniband/core/ucma.c b/drivers/infiniband/core/ucma.c
> index 5b87eee8ccc8b6..d03dacaef78805 100644
> --- a/drivers/infiniband/core/ucma.c
> +++ b/drivers/infiniband/core/ucma.c
> @@ -1084,6 +1084,8 @@ static ssize_t ucma_connect(struct ucma_file *file, const char __user *inbuf,
>  	size_t in_size;
>  	int ret;
>
> +	if (in_len < offsetofend(typeof(cmd), reserved))
> +		return -EINVAL;

This check wasn't before the patches citied in Fixes lines. This is why
I didn't add them while extended ucma_*.

>  	in_size = min_t(size_t, in_len, sizeof(cmd));
>  	if (copy_from_user(&cmd, inbuf, in_size))
>  		return -EFAULT;
> @@ -1141,6 +1143,8 @@ static ssize_t ucma_accept(struct ucma_file *file, const char __user *inbuf,
>  	size_t in_size;
>  	int ret;
>
> +	if (in_len < offsetofend(typeof(cmd), reserved))
> +		return -EINVAL;
>  	in_size = min_t(size_t, in_len, sizeof(cmd));
>  	if (copy_from_user(&cmd, inbuf, in_size))
>  		return -EFAULT;
> --
> 2.27.0
>

  reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-24 13:19 Jason Gunthorpe
2020-07-24 13:45 ` Leon Romanovsky [this message]
2020-07-24 13:52   ` Jason Gunthorpe
2020-07-24 19:33     ` Leon Romanovsky
2020-07-24 19:33 ` Leon Romanovsky
2020-07-27 14:57 ` Jason Gunthorpe

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