Bug 2265792 (CVE-2023-52456)

Summary:	CVE-2023-52456 kernel: imx: fix tx statemachine deadlock
Product:	[Other] Security Response	Reporter:	Patrick Del Bello <pdelbell>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	acaringi, allarkin, aquini, bhu, chwhite, cye, cyin, dbohanno, debarbos, dfreiber, drow, dvlasenk, esandeen, ezulian, hkrzesin, jarod, jburrell, jdenham, jfaracco, jforbes, jlelli, joe.lawrence, jshortt, jstancek, jwyatt, kcarcia, ldoskova, lgoncalv, lzampier, mleitner, mmilgram, mstowell, nmurray, ptalbert, rparrazo, rrobaina, rvrbovsk, rysulliv, scweaver, sukulkar, tglozar, tyberry, vkumar, wcosta, williams, wmealing, ycote, ykopkova, zhijwang
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:	kernel 6.8-rc1	Doc Type:	If docs needed, set a value
Doc Text:	A flaw was found in the UART driver handling RS485 communication in the Linux Kernel when an unexpected closure of the TTY port occurs, such as during a userland application crash. In this scenario, the imx_uart_shutdown function disables the UART interface and the Transmission Complete (TC) interrupt. Subsequently, the imx_uart_stop_tx function attempts to stop the transmission but exits prematurely if the transmission is incomplete, expecting the now-disabled TC interrupt to complete the process. This results in the transmission state machine remaining in a deadlocked SEND state, leaving the TX_EN pin low and rendering the RS485 interface non-functional. This vulnerability can lead to communication failures and potential system instability.	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:	2265804
Bug Blocks:	2265790

Description Patrick Del Bello 2024-02-24 11:19:56 UTC

When using the serial port as RS485 port, the tx statemachine is used to
control the RTS pin to drive the RS485 transceiver TX_EN pin. When the
TTY port is closed in the middle of a transmission (for instance during
userland application crash), imx_uart_shutdown disables the interface
and disables the Transmission Complete interrupt. afer that,
imx_uart_stop_tx bails on an incomplete transmission, to be retriggered
by the TC interrupt. This interrupt is disabled and therefore the tx
statemachine never transitions out of SEND. The statemachine is in
deadlock now, and the TX_EN remains low, making the interface useless.

imx_uart_stop_tx now checks for incomplete transmission AND whether TC
interrupts are enabled before bailing to be retriggered. This makes sure
the state machine handling is reached, and is properly set to
WAIT_AFTER_SEND.

Comment 1 Patrick Del Bello 2024-02-24 11:24:28 UTC

Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 2265804]

Comment 3 Justin M. Forbes 2024-02-27 00:21:15 UTC

	Issue introduced in 5.9 with commit cb1a60923609 and fixed in 5.10.209 with commit 6e04a9d30509
	Issue introduced in 5.9 with commit cb1a60923609 and fixed in 5.15.148 with commit ff168d4fdb0e
	Issue introduced in 5.9 with commit cb1a60923609 and fixed in 6.1.75 with commit 63ee7be01a3f
	Issue introduced in 5.9 with commit cb1a60923609 and fixed in 6.6.14 with commit 763cd6874631
	Issue introduced in 5.9 with commit cb1a60923609 and fixed in 6.7.2 with commit 9a662d06c22d
	Issue introduced in 5.9 with commit cb1a60923609 and fixed in 6.8-rc1 with commit 78d60dae9a0c

Comment 4 Justin M. Forbes 2024-02-27 00:21:48 UTC

This was fixed for Fedora with the 6.6.14 stable kernel updates.

Comment 8 Alex 2024-06-09 15:14:13 UTC

The result of automatic check (that is developed by Alexander Larkin) for this CVE-2023-52456 is: CHECK	Maybe valid. Check manually. with impact MODERATE (that is approximation based on flags DEADLOCK DANGER PRINTF-TTY IMPROVEONLY  ; these flags parsed automatically based on patche data). Such automatic check happens only for Low/Moderates (and only when not from reporter, but parsing already existing CVE). Highs always checked manually (I check it myself and then we check it again in Remediation team). In rare cases some of the Moderates could be increased to High later.