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Date:   Mon, 20 Nov 2023 17:31:53 +0200
From:   =?UTF-8?Q?Jos=C3=A9_Pekkarinen?= <jose.pekkarinen@foxhound.fi>
To:     viro@zeniv.linux.org.uk, skhan@linuxfoundation.org
Cc:     linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linux.dev,
        syzbot+cb729843d0f42a5c1a50@syzkaller.appspotmail.com
Subject: Re: [PATCH] iov_iter: fix memleak in iov_iter_extract_pages
In-Reply-To: <20231111075323.208181-1-jose.pekkarinen@foxhound.fi>
References: <20231111075323.208181-1-jose.pekkarinen@foxhound.fi>
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On 2023-11-11 09:53, José Pekkarinen wrote:
> syzbot reports there is a memory leak in iov_iter_extract_pages where 
> in
> the unlikely case of having an error in pin_user_pages_fast, the pages
> aren't free. This patch will free it before returning. Output of mem
> leak follows:
> 
> BUG: memory leak
> unreferenced object 0xffff888109d2e400 (size 1024):
>   comm "syz-executor121", pid 5006, jiffies 4294943225 (age 17.760s)
>   hex dump (first 32 bytes):
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<ffffffff81554bbb>] __do_kmalloc_node mm/slab_common.c:984 
> [inline]
>     [<ffffffff81554bbb>] __kmalloc_node+0x4b/0x150 mm/slab_common.c:992
>     [<ffffffff815440f9>] kmalloc_node include/linux/slab.h:602 [inline]
>     [<ffffffff815440f9>] kvmalloc_node+0x99/0x170 mm/util.c:604
>     [<ffffffff824c52fe>] kvmalloc include/linux/slab.h:720 [inline]
>     [<ffffffff824c52fe>] kvmalloc_array include/linux/slab.h:738 
> [inline]
>     [<ffffffff824c52fe>] want_pages_array lib/iov_iter.c:985 [inline]
>     [<ffffffff824c52fe>] iov_iter_extract_user_pages
> lib/iov_iter.c:1765 [inline]
>     [<ffffffff824c52fe>] iov_iter_extract_pages+0x1ee/0xa40 
> lib/iov_iter.c:1831
>     [<ffffffff824125a7>] bio_map_user_iov+0x167/0x5d0 
> block/blk-map.c:297
>     [<ffffffff82412df3>] blk_rq_map_user_iov+0x3e3/0xb30 
> block/blk-map.c:664
>     [<ffffffff82413943>] blk_rq_map_user block/blk-map.c:691 [inline]
>     [<ffffffff82413943>] blk_rq_map_user_io+0x143/0x160 
> block/blk-map.c:724
>     [<ffffffff82ca0925>] sg_io+0x285/0x510 
> drivers/scsi/scsi_ioctl.c:456
>     [<ffffffff82ca1025>] scsi_cdrom_send_packet+0x1b5/0x480
> drivers/scsi/scsi_ioctl.c:820
>     [<ffffffff82ca13ba>] scsi_ioctl+0xca/0xd30 
> drivers/scsi/scsi_ioctl.c:903
>     [<ffffffff82d35964>] sg_ioctl+0x5f4/0x10a0 drivers/scsi/sg.c:1163
>     [<ffffffff8168e602>] vfs_ioctl fs/ioctl.c:51 [inline]
>     [<ffffffff8168e602>] __do_sys_ioctl fs/ioctl.c:870 [inline]
>     [<ffffffff8168e602>] __se_sys_ioctl fs/ioctl.c:856 [inline]
>     [<ffffffff8168e602>] __x64_sys_ioctl+0xf2/0x140 fs/ioctl.c:856
>     [<ffffffff84ad2bb8>] do_syscall_x64 arch/x86/entry/common.c:50 
> [inline]
>     [<ffffffff84ad2bb8>] do_syscall_64+0x38/0xb0 
> arch/x86/entry/common.c:80
>     [<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> BUG: memory leak
> unreferenced object 0xffff888109d2dc00 (size 1024):
>   comm "syz-executor121", pid 5007, jiffies 4294943747 (age 12.540s)
>   hex dump (first 32 bytes):
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<ffffffff81554bbb>] __do_kmalloc_node mm/slab_common.c:984 
> [inline]
>     [<ffffffff81554bbb>] __kmalloc_node+0x4b/0x150 mm/slab_common.c:992
>     [<ffffffff815440f9>] kmalloc_node include/linux/slab.h:602 [inline]
>     [<ffffffff815440f9>] kvmalloc_node+0x99/0x170 mm/util.c:604
>     [<ffffffff824c52fe>] kvmalloc include/linux/slab.h:720 [inline]
>     [<ffffffff824c52fe>] kvmalloc_array include/linux/slab.h:738 
> [inline]
>     [<ffffffff824c52fe>] want_pages_array lib/iov_iter.c:985 [inline]
>     [<ffffffff824c52fe>] iov_iter_extract_user_pages
> lib/iov_iter.c:1765 [inline]
>     [<ffffffff824c52fe>] iov_iter_extract_pages+0x1ee/0xa40 
> lib/iov_iter.c:1831
>     [<ffffffff824125a7>] bio_map_user_iov+0x167/0x5d0 
> block/blk-map.c:297
>     [<ffffffff82412df3>] blk_rq_map_user_iov+0x3e3/0xb30 
> block/blk-map.c:664
>     [<ffffffff82413943>] blk_rq_map_user block/blk-map.c:691 [inline]
>     [<ffffffff82413943>] blk_rq_map_user_io+0x143/0x160 
> block/blk-map.c:724
>     [<ffffffff82ca0925>] sg_io+0x285/0x510 
> drivers/scsi/scsi_ioctl.c:456
>     [<ffffffff82ca1025>] scsi_cdrom_send_packet+0x1b5/0x480
> drivers/scsi/scsi_ioctl.c:820
>     [<ffffffff82ca13ba>] scsi_ioctl+0xca/0xd30 
> drivers/scsi/scsi_ioctl.c:903
>     [<ffffffff82d35964>] sg_ioctl+0x5f4/0x10a0 drivers/scsi/sg.c:1163
>     [<ffffffff8168e602>] vfs_ioctl fs/ioctl.c:51 [inline]
>     [<ffffffff8168e602>] __do_sys_ioctl fs/ioctl.c:870 [inline]
>     [<ffffffff8168e602>] __se_sys_ioctl fs/ioctl.c:856 [inline]
>     [<ffffffff8168e602>] __x64_sys_ioctl+0xf2/0x140 fs/ioctl.c:856
>     [<ffffffff84ad2bb8>] do_syscall_x64 arch/x86/entry/common.c:50 
> [inline]
>     [<ffffffff84ad2bb8>] do_syscall_64+0x38/0xb0 
> arch/x86/entry/common.c:80
>     [<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> BUG: memory leak
> unreferenced object 0xffff888109d2d800 (size 1024):
>   comm "syz-executor121", pid 5010, jiffies 4294944269 (age 7.320s)
>   hex dump (first 32 bytes):
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<ffffffff81554bbb>] __do_kmalloc_node mm/slab_common.c:984 
> [inline]
>     [<ffffffff81554bbb>] __kmalloc_node+0x4b/0x150 mm/slab_common.c:992
>     [<ffffffff815440f9>] kmalloc_node include/linux/slab.h:602 [inline]
>     [<ffffffff815440f9>] kvmalloc_node+0x99/0x170 mm/util.c:604
>     [<ffffffff824c52fe>] kvmalloc include/linux/slab.h:720 [inline]
>     [<ffffffff824c52fe>] kvmalloc_array include/linux/slab.h:738 
> [inline]
>     [<ffffffff824c52fe>] want_pages_array lib/iov_iter.c:985 [inline]
>     [<ffffffff824c52fe>] iov_iter_extract_user_pages
> lib/iov_iter.c:1765 [inline]
>     [<ffffffff824c52fe>] iov_iter_extract_pages+0x1ee/0xa40 
> lib/iov_iter.c:1831
>     [<ffffffff824125a7>] bio_map_user_iov+0x167/0x5d0 
> block/blk-map.c:297
>     [<ffffffff82412df3>] blk_rq_map_user_iov+0x3e3/0xb30 
> block/blk-map.c:664
>     [<ffffffff82413943>] blk_rq_map_user block/blk-map.c:691 [inline]
>     [<ffffffff82413943>] blk_rq_map_user_io+0x143/0x160 
> block/blk-map.c:724
>     [<ffffffff82ca0925>] sg_io+0x285/0x510 
> drivers/scsi/scsi_ioctl.c:456
>     [<ffffffff82ca1025>] scsi_cdrom_send_packet+0x1b5/0x480
> drivers/scsi/scsi_ioctl.c:820
>     [<ffffffff82ca13ba>] scsi_ioctl+0xca/0xd30 
> drivers/scsi/scsi_ioctl.c:903
>     [<ffffffff82d35964>] sg_ioctl+0x5f4/0x10a0 drivers/scsi/sg.c:1163
>     [<ffffffff8168e602>] vfs_ioctl fs/ioctl.c:51 [inline]
>     [<ffffffff8168e602>] __do_sys_ioctl fs/ioctl.c:870 [inline]
>     [<ffffffff8168e602>] __se_sys_ioctl fs/ioctl.c:856 [inline]
>     [<ffffffff8168e602>] __x64_sys_ioctl+0xf2/0x140 fs/ioctl.c:856
>     [<ffffffff84ad2bb8>] do_syscall_x64 arch/x86/entry/common.c:50 
> [inline]
>     [<ffffffff84ad2bb8>] do_syscall_64+0x38/0xb0 
> arch/x86/entry/common.c:80
>     [<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> Reported-by: syzbot+cb729843d0f42a5c1a50@syzkaller.appspotmail.com
> Closes:
> https://syzkaller.appspot.com/bug?id=99c8551967f413d108cfdd2950a0cb5652de07b8
> Fixes: 7d58fe7310281 ("iov_iter: Add a function to extract a page list
> from an iterator")
> Signed-off-by: José Pekkarinen <jose.pekkarinen@foxhound.fi>
> ---
>  lib/iov_iter.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/iov_iter.c b/lib/iov_iter.c
> index 27234a820eeb..c3fd0448dead 100644
> --- a/lib/iov_iter.c
> +++ b/lib/iov_iter.c
> @@ -1780,8 +1780,10 @@ static ssize_t
> iov_iter_extract_user_pages(struct iov_iter *i,
>  	if (!maxpages)
>  		return -ENOMEM;
>  	res = pin_user_pages_fast(addr, maxpages, gup_flags, *pages);
> -	if (unlikely(res <= 0))
> +	if (unlikely(res <= 0)) {
> +		kvfree(*pages);
>  		return res;
> +	}
>  	maxsize = min_t(size_t, maxsize, res * PAGE_SIZE - offset);
>  	iov_iter_advance(i, maxsize);
>  	return maxsize;

     Ping.

     José.