linux-kernel - [PATCH] loop: mask loop_control

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Date:   Thu, 18 Nov 2021 10:36:40 +0800
From:   wangyangbo <yangbonis@...oud.com>
To:     axboe@...nel.dk
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        wangyangbo <yangbonis@...oud.com>
Subject: [PATCH] loop: mask loop_control_ioctl parameter only as minor

From: wangyangbo <wangyangbo@...ontech.com>

loop_control_ioctl call add_disk of block layer, but may pass number beyond MAX MINOR.
So mask loop_control_ioctl parameter only as minor.

Reproduce:
touch file
losetup /dev/loop1048576 file
losetup /dev/loop0 file

Problem:
sysfs: cannot create duplicate filename '/dev/block/7:0'
CPU: 0 PID: 529 Comm: losetup Not tainted 5.14.16-arch1-1 #1 ad87b876fa2ab6fdbd995dc1c9aab0ad8f767b2c
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
Call Trace:
 dump_stack_lvl+0x46/0x5a
 sysfs_warn_dup.cold+0x17/0x24
 sysfs_do_create_link_sd+0xbe/0xd0
 device_add+0x580/0x970
 ? dev_set_name+0x5b/0x80
 __device_add_disk+0xb5/0x2f0
 loop_add+0x236/0x290 [loop 2ed923fc8fbd84fdc093bf55ac085973636a3936]
 loop_control_ioctl+0x7f/0x1f0 [loop 2ed923fc8fbd84fdc093bf55ac085973636a3936]
 __x64_sys_ioctl+0x82/0xb0
 do_syscall_64+0x5c/0x80
 ? syscall_exit_to_user_mode+0x23/0x40
 ? do_syscall_64+0x69/0x80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7ff3e8ba259b
Code: ff ff ff 85 c0 79 9b 49 c7 c4 ff ff ff ff 5b 5d 4c 89 e0 41 5c c3 66 0f 1f 84 00 00 00 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d a5 a8 0c 00 f7 d8 64 89 01 48
RSP: 002b:00007ffe6d2eaa18 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ffe6d2eb038 RCX: 00007ff3e8ba259b
RDX: 0000000000000000 RSI: 0000000000004c80 RDI: 0000000000000003
RBP: 00007ffe6d2eaae0 R08: 1999999999999999 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
R13: 00007ffe6d2eaa24 R14: 0000560b131bd200 R15: 0000560b131c44a0
---
 drivers/block/loop.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index a154cab6cd98..0d8240a7e66d 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -2170,11 +2170,11 @@ static long loop_control_ioctl(struct file *file, unsigned int cmd,
 {
 	switch (cmd) {
 	case LOOP_CTL_ADD:
-		return loop_add(parm);
+		return loop_add(MINOR(parm));
 	case LOOP_CTL_REMOVE:
-		return loop_control_remove(parm);
+		return loop_control_remove(MINOR(parm));
 	case LOOP_CTL_GET_FREE:
-		return loop_control_get_free(parm);
+		return loop_control_get_free(MINOR(parm));
 	default:
 		return -ENOSYS;
 	}
-- 
2.20.1