[PATCH] udmabuf: Set the DMA mask for the udmabuf device

[Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>]

If the DMA mask is not set explicitly, the following warning occurs
when the userspace tries to access the dma-buf via the CPU as
reported by syzbot here:

WARNING: CPU: 1 PID: 3595 at kernel/dma/mapping.c:188
__dma_map_sg_attrs+0x181/0x1f0 kernel/dma/mapping.c:188
Modules linked in:
CPU: 0 PID: 3595 Comm: syz-executor249 Not tainted
5.17.0-rc2-syzkaller-00316-g0457e5153e0e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:__dma_map_sg_attrs+0x181/0x1f0 kernel/dma/mapping.c:188
Code: 00 00 00 00 00 fc ff df 48 c1 e8 03 80 3c 10 00 75 71 4c 8b 3d c0
83 b5 0d e9 db fe ff ff e8 b6 0f 13 00 0f 0b e8 af 0f 13 00 <0f> 0b 45
   31 e4 e9 54 ff ff ff e8 a0 0f 13 00 49 8d 7f 50 48 b8 00
RSP: 0018:ffffc90002a07d68 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff88807e25e2c0 RSI: ffffffff81649e91 RDI: ffff88801b848408
RBP: ffff88801b848000 R08: 0000000000000002 R09: ffff88801d86c74f
R10: ffffffff81649d72 R11: 0000000000000001 R12: 0000000000000002
R13: ffff88801d86c680 R14: 0000000000000001 R15: 0000000000000000
FS:  0000555556e30300(0000) GS:ffff8880b9d00000(0000)
knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000200000cc CR3: 000000001d74a000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 dma_map_sgtable+0x70/0xf0 kernel/dma/mapping.c:264
 get_sg_table.isra.0+0xe0/0x160 drivers/dma-buf/udmabuf.c:72
 begin_cpu_udmabuf+0x130/0x1d0 drivers/dma-buf/udmabuf.c:126
 dma_buf_begin_cpu_access+0xfd/0x1d0 drivers/dma-buf/dma-buf.c:1164
 dma_buf_ioctl+0x259/0x2b0 drivers/dma-buf/dma-buf.c:363
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl fs/ioctl.c:860 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f62fcf530f9
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89
f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01
f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe3edab9b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f62fcf530f9
RDX: 0000000020000200 RSI: 0000000040086200 RDI: 0000000000000006
RBP: 00007f62fcf170e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f62fcf17170
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>

Reported-by: syzbot+10e27961f4da37c443b2 at syzkaller.appspotmail.com
Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>
---
 drivers/dma-buf/udmabuf.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index e7330684d3b8..8f9aab9ece32 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -365,7 +365,22 @@ static struct miscdevice udmabuf_misc = {
 
 static int __init udmabuf_dev_init(void)
 {
-	return misc_register(&udmabuf_misc);
+	int ret;
+
+	ret = misc_register(&udmabuf_misc);
+	if (ret < 0) {
+		pr_err("Could not initialize udmabuf device\n");
+		return ret;
+	}
+
+	ret = dma_coerce_mask_and_coherent(udmabuf_misc.this_device,
+					   DMA_BIT_MASK(64));
+	if (ret < 0) {
+		pr_err("Could not setup DMA mask for udmabuf device\n");
+		return ret;
+	}
+
+	return 0;
 }
 
 static void __exit udmabuf_dev_exit(void)
-- 
2.35.1