From 545a32498c536ee152331cd2e7d2416aa0f20e01 Mon Sep 17 00:00:00 2001

From: Xiongwei Song <sxwjean@gmail.com>

Date: Tue, 16 Nov 2021 21:10:33 +0800

Subject: [PATCH] floppy: Add max size check for user space request

Git-commit: 545a32498c536ee152331cd2e7d2416aa0f20e01

Patch-mainline: v5.17-rc1

References: git-fixes

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>

Acked-by: Takashi Iwai <tiwai@suse.de>

---

 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 f0e36c18f349..e611411a934c 100644

--- a/drivers/block/floppy.c

+++ b/drivers/block/floppy.c

@@ -3081,6 +3081,8 @@ 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)

 {

@@ -3108,7 +3110,7 @@ static int raw_cmd_copyin(int cmd, void __user *param,

 	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);

-- 

2.31.1