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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot+23a02c7df2cf2bc93fa2@syzkaller.appspotmail.com,
        Xiongwei Song <sxwjean@gmail.com>,
        Denis Efremov <efremov@linux.com>,
        Jens Axboe <axboe@kernel.dk>, Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.15 520/846] floppy: Add max size check for user space request
Date:   Mon, 24 Jan 2022 19:40:37 +0100
Message-Id: <20220124184118.952832171@linuxfoundation.org>
In-Reply-To: <20220124184100.867127425@linuxfoundation.org>
References: <20220124184100.867127425@linuxfoundation.org>
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From: Xiongwei Song <sxwjean@gmail.com>

[ Upstream commit 545a32498c536ee152331cd2e7d2416aa0f20e01 ]

We need to check the max request size that is from user space before
allocating pages. If the request size exceeds the limit, return -EINVAL.
This check can avoid the warning below from page allocator.

WARNING: CPU: 3 PID: 16525 at mm/page_alloc.c:5344 current_gfp_context include/linux/sched/mm.h:195 [inline]
WARNING: CPU: 3 PID: 16525 at mm/page_alloc.c:5344 __alloc_pages+0x45d/0x500 mm/page_alloc.c:5356
Modules linked in:
CPU: 3 PID: 16525 Comm: syz-executor.3 Not tainted 5.15.0-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
RIP: 0010:__alloc_pages+0x45d/0x500 mm/page_alloc.c:5344
Code: be c9 00 00 00 48 c7 c7 20 4a 97 89 c6 05 62 32 a7 0b 01 e8 74 9a 42 07 e9 6a ff ff ff 0f 0b e9 a0 fd ff ff 40 80 e5 3f eb 88 <0f> 0b e9 18 ff ff ff 4c 89 ef 44 89 e6 45 31 ed e8 1e 76 ff ff e9
RSP: 0018:ffffc90023b87850 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 1ffff92004770f0b RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000033 RDI: 0000000000010cc1
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
R10: ffffffff81bb4686 R11: 0000000000000001 R12: ffffffff902c1960
R13: 0000000000000033 R14: 0000000000000000 R15: ffff88804cf64a30
FS:  0000000000000000(0000) GS:ffff88802cd00000(0063) knlGS:00000000f44b4b40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 000000002c921000 CR3: 000000004f507000 CR4: 0000000000150ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 alloc_pages+0x1a7/0x300 mm/mempolicy.c:2191
 __get_free_pages+0x8/0x40 mm/page_alloc.c:5418
 raw_cmd_copyin drivers/block/floppy.c:3113 [inline]
 raw_cmd_ioctl drivers/block/floppy.c:3160 [inline]
 fd_locked_ioctl+0x12e5/0x2820 drivers/block/floppy.c:3528
 fd_ioctl drivers/block/floppy.c:3555 [inline]
 fd_compat_ioctl+0x891/0x1b60 drivers/block/floppy.c:3869
 compat_blkdev_ioctl+0x3b8/0x810 block/ioctl.c:662
 __do_compat_sys_ioctl+0x1c7/0x290 fs/ioctl.c:972
 do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
 __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178
 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c

Reported-by: syzbot+23a02c7df2cf2bc93fa2@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/20211116131033.27685-1-sxwjean@me.com
Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
Signed-off-by: Denis Efremov <efremov@linux.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/block/floppy.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index f50bbaba5762c..4a6a74177b3c9 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -3080,6 +3080,8 @@ static void raw_cmd_free(struct floppy_raw_cmd **ptr)
 	}
 }
 
+#define MAX_LEN (1UL << MAX_ORDER << PAGE_SHIFT)
+
 static int raw_cmd_copyin(int cmd, void __user *param,
 				 struct floppy_raw_cmd **rcmd)
 {
@@ -3107,7 +3109,7 @@ loop:
 	ptr->resultcode = 0;
 
 	if (ptr->flags & (FD_RAW_READ | FD_RAW_WRITE)) {
-		if (ptr->length <= 0)
+		if (ptr->length <= 0 || ptr->length >= MAX_LEN)
 			return -EINVAL;
 		ptr->kernel_data = (char *)fd_dma_mem_alloc(ptr->length);
 		fallback_on_nodma_alloc(&ptr->kernel_data, ptr->length);
-- 
2.34.1