[PATCH] Staging: unisys: verify that a control channel exists
From: Sasha Levin
Date: Fri Apr 04 2014 - 14:38:48 EST
The code didn't verify that a control channel exists before trying to
use it. It caused NULL ptr derefs which were easy to trigger by an
unpriviliged user simply by reading the proc file, causing:
[ 68.161404] BUG: unable to handle kernel NULL pointer dereference at (null)
[ 68.162442] IP: visorchannel_read (drivers/staging/unisys/visorchannel/visorchannel_funcs.c:225)
[ 68.163165] PGD 5ca21067 PUD 5ca20067 PMD 0
[ 68.163712] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
[ 68.164390] Dumping ftrace buffer:
[ 68.164793] (ftrace buffer empty)
[ 68.165220] Modules linked in:
[ 68.165601] CPU: 0 PID: 7915 Comm: cat Tainted: G W 3.14.0-next-20140403-sasha-00012-gef5fa7d-dirty #373
[ 68.166821] task: ffff88006e8c3000 ti: ffff88005ca30000 task.ti: ffff88005ca30000
[ 68.167689] RIP: visorchannel_read (drivers/staging/unisys/visorchannel/visorchannel_funcs.c:225)
[ 68.168683] RSP: 0018:ffff88005ca31e58 EFLAGS: 00010282
[ 68.169302] RAX: ffff88005ca10000 RBX: ffff88005ca31e97 RCX: 0000000000000001
[ 68.170019] RDX: ffff88005ca31e97 RSI: 0000000000000bd6 RDI: 0000000000000000
[ 68.170019] RBP: ffff88005ca31e78 R08: 0000000000000000 R09: 0000000000000000
[ 68.170019] R10: ffff880000000000 R11: 0000000000000001 R12: 0000000000000001
[ 68.170019] R13: 0000000000000bd6 R14: 0000000000000000 R15: 0000000000008000
[ 68.170019] FS: 00007f0e8c041700(0000) GS:ffff88007be00000(0000) knlGS:0000000000000000
[ 68.170019] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 68.170019] CR2: 0000000000000000 CR3: 000000006efe9000 CR4: 00000000000006b0
[ 68.170019] Stack:
[ 68.170019] ffff88005ca31f50 ffff88005ca10000 000000000060e000 ffff88005ca31f50
[ 68.170019] ffff88005ca31ec8 ffffffff83e6f983 ffff8800780db810 0000000000008000
[ 68.170019] ffff88005ca31ec8 ffff88006da5f908 ffff8800780db800 000000000060e000
[ 68.170019] Call Trace:
[ 68.170019] proc_read_toolaction (drivers/staging/unisys/visorchipset/visorchipset_main.c:2541)
[ 68.170019] proc_reg_read (fs/proc/inode.c:211)
[ 68.170019] vfs_read (fs/read_write.c:408)
[ 68.170019] SyS_read (fs/read_write.c:519 fs/read_write.c:511)
[ 68.170019] tracesys (arch/x86/kernel/entry_64.S:749)
[ 68.170019] Code: 00 00 66 66 66 66 90 55 48 89 e5 48 83 ec 20 48 89 5d e0 48 89 d3 4c 89 65 e8 49 89 cc 4c 89 6d f0 49 89 f5 4c 89 75 f8 49 89 fe <48> 8b 3f e8 4f f9 ff ff 85 c0 0f 88 97 00 00 00 4d 85 ed 0f 85
[ 68.170019] RIP visorchannel_read (drivers/staging/unisys/visorchannel/visorchannel_funcs.c:225)
[ 68.170019] RSP <ffff88005ca31e58>
[ 68.170019] CR2: 0000000000000000
Signed-off-by: Sasha Levin <sasha.levin@xxxxxxxxxx>
---
.../staging/unisys/visorchipset/visorchipset_main.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/drivers/staging/unisys/visorchipset/visorchipset_main.c b/drivers/staging/unisys/visorchipset/visorchipset_main.c
index 8252ca1..257c6e5 100644
--- a/drivers/staging/unisys/visorchipset/visorchipset_main.c
+++ b/drivers/staging/unisys/visorchipset/visorchipset_main.c
@@ -2414,6 +2414,9 @@ proc_read_installer(struct file *file, char __user *buf,
char *vbuf;
loff_t pos = *offset;
+ if (!ControlVm_channel)
+ return -ENODEV;
+
if (pos < 0)
return -EINVAL;
@@ -2463,6 +2466,9 @@ proc_write_installer(struct file *file,
U16 remainingSteps;
U32 error, textId;
+ if (!ControlVm_channel)
+ return -ENODEV;
+
/* Check to make sure there is no buffer overflow */
if (count > (sizeof(buf) - 1))
return -EINVAL;
@@ -2524,6 +2530,9 @@ proc_read_toolaction(struct file *file, char __user *buf,
char *vbuf;
loff_t pos = *offset;
+ if (!ControlVm_channel)
+ return -ENODEV;
+
if (pos < 0)
return -EINVAL;
@@ -2562,6 +2571,9 @@ proc_write_toolaction(struct file *file,
char buf[3];
U8 toolAction;
+ if (!ControlVm_channel)
+ return -ENODEV;
+
/* Check to make sure there is no buffer overflow */
if (count > (sizeof(buf) - 1))
return -EINVAL;
@@ -2601,6 +2613,9 @@ proc_read_bootToTool(struct file *file, char __user *buf,
char *vbuf;
loff_t pos = *offset;
+ if (!ControlVm_channel)
+ return -ENODEV;
+
if (pos < 0)
return -EINVAL;
@@ -2639,6 +2654,9 @@ proc_write_bootToTool(struct file *file,
int inputVal;
ULTRA_EFI_SPAR_INDICATION efiSparIndication;
+ if (!ControlVm_channel)
+ return -ENODEV;
+
/* Check to make sure there is no buffer overflow */
if (count > (sizeof(buf) - 1))
return -EINVAL;
--
1.7.10.4
--
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