Bug 2144379 (CVE-2022-41858)

Summary:	CVE-2022-41858 kernel: null-ptr-deref vulnerabilities in sl_tx_timeout in drivers/net/slip
Product:	[Other] Security Response	Reporter:	Rohit Keshri <rkeshri>
Component:	vulnerability	Assignee:	Nobody <nobody>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	acaringi, adscvr, airlied, alciregi, bhu, brdeoliv, bskeggs, chwhite, ddepaula, debarbos, dvlasenk, ezulian, hdegoede, hkrzesin, hpa, jarod, jarodwilson, jburrell, jfaracco, jferlan, jforbes, jglisse, jlelli, joe.lawrence, jonathan, josef, jshortt, jstancek, jwboyer, jwyatt, kcarcia, kernel-maint, kernel-mgr, lgoncalv, linville, lleshchi, lzampier, masami256, mchehab, nmurray, ptalbert, qzhao, rvrbovsk, scweaver, steved, swood, tyberry, vkumar, walters, williams
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	kernel 5.18 rc2	Doc Type:	If docs needed, set a value
Doc Text:	A flaw was found in the Linux kernel. A NULL pointer dereference may occur while a slip driver is in progress to detach in sl_tx_timeout in drivers/net/slip/slip.c. This issue could allow an attacker to crash the system or leak internal kernel information.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2144390, 2144391, 2144392, 2144393
Bug Blocks:	2144381, 2144843

Description Rohit Keshri 2022-11-21 04:02:58 UTC

There are null-ptr-deref vulnerabilities in drivers/net/slip of linux that allow attacker to
crash linux kernel by simulating slip network card from user-space of linux.

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[Root cause]

When a slip driver is detaching, the slip_close() will act to
cleanup necessary resources and sl->tty is set to NULL in
slip_close(). Meanwhile, the packet we transmit is blocked,
sl_tx_timeout() will be called. Although slip_close() and
sl_tx_timeout() use sl->lock to synchronize, we don`t judge
whether sl->tty equals to NULL in sl_tx_timeout() and the
null pointer dereference bug will happen.

(Thread 1) | (Thread 2)
| slip_close()
| spin_lock_bh(&sl->lock)
| ...
... | sl->tty = NULL //(1)
sl_tx_timeout() | spin_unlock_bh(&sl->lock)
spin_lock(&sl->lock); |
... | ...
tty_chars_in_buffer(sl->tty)|
if (tty->ops->..) //(2) |
... | synchronize_rcu()

We set NULL to sl->tty in position (1) and dereference sl->tty
in position (2).

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