ACK: [SRU][M/J][PATCH 0/1] CVE-2024-26893

[Tim Gardner]

On 5/7/24 21:31, Bethany Jamison wrote:
> [Impact]
> 
>   In the Linux kernel, the following vulnerability has been resolved:
> 
>   firmware: arm_scmi: Fix double free in SMC transport cleanup path
> 
>   When the generic SCMI code tears down a channel, it calls the chan_free
>   callback function, defined by each transport. Since multiple protocols
>   might share the same transport_info member, chan_free() might want to
>   clean up the same member multiple times within the given SCMI transport
>   implementation. In this case, it is SMC transport. This will lead to a NULL
>   pointer dereference at the second time:
> 
>       | scmi_protocol scmi_dev.1: Enabled polling mode TX channel -
>   prot_id:16
>       | arm-scmi firmware:scmi: SCMI Notifications - Core Enabled.
>       | arm-scmi firmware:scmi: unable to communicate with SCMI
>       | Unable to handle kernel NULL pointer dereference at virtual address
>   0000000000000000
>       | Mem abort info:
>       |   ESR = 0x0000000096000004
>       |   EC = 0x25: DABT (current EL), IL = 32 bits
>       |   SET = 0, FnV = 0
>       |   EA = 0, S1PTW = 0
>       |   FSC = 0x04: level 0 translation fault
>       | Data abort info:
>       |   ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000
>       |   CM = 0, WnR = 0, TnD = 0, TagAccess = 0
>       |   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
>       | user pgtable: 4k pages, 48-bit VAs, pgdp=0000000881ef8000
>       | [0000000000000000] pgd=0000000000000000, p4d=0000000000000000
>       | Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
>       | Modules linked in:
>       | CPU: 4 PID: 1 Comm: swapper/0 Not tainted
> 6.7.0-rc2-00124-g455ef3d016c9-dirty #793
>       | Hardware name: FVP Base RevC (DT)
>       | pstate: 61400009 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
>       | pc : smc_chan_free+0x3c/0x6c
>       | lr : smc_chan_free+0x3c/0x6c
>       | Call trace:
>       |  smc_chan_free+0x3c/0x6c
>       |  idr_for_each+0x68/0xf8
>       |  scmi_cleanup_channels.isra.0+0x2c/0x58
>       |  scmi_probe+0x434/0x734
>       |  platform_probe+0x68/0xd8
>       |  really_probe+0x110/0x27c
>       |  __driver_probe_device+0x78/0x12c
>       |  driver_probe_device+0x3c/0x118
>       |  __driver_attach+0x74/0x128
>       |  bus_for_each_dev+0x78/0xe0
>       |  driver_attach+0x24/0x30
>       |  bus_add_driver+0xe4/0x1e8
>       |  driver_register+0x60/0x128
>       |  __platform_driver_register+0x28/0x34
>       |  scmi_driver_init+0x84/0xc0
>       |  do_one_initcall+0x78/0x33c
>       |  kernel_init_freeable+0x2b8/0x51c
>       |  kernel_init+0x24/0x130
>       |  ret_from_fork+0x10/0x20
>       | Code: f0004701 910a0021 aa1403e5 97b91c70 (b9400280)
>       | ---[ end trace 0000000000000000 ]---
> 
>   Simply check for the struct pointer being NULL before trying to access
>   its members, to avoid this situation.
> 
>   This was found when a transport doesn't really work (for instance no SMC
>   service), the probe routines then tries to clean up, and triggers a crash.
> 
> [Fix]
> 
> Mantic:	Clean cherry-pick from linux-6.6.y
> Jammy:	Backported - I added the if-statement from the fix commit as is
> 	ignoring the context conflict (missing free_irq if-statement).
> Focal:	not-affected
> Bionic:	not-affected
> Xenial:	not-affected
> Trusty:	not-affected
> 
> [Test Case]
> 
> Compile and boot tested.
> 
> [Where problems could occur]
> 
> This fix affects those who use the ARM SCMI (System Control and
> Management Interface) driver, an issue with this fix would be visable to
> the user via a system crash.
> 
> Andre Przywara (1):
>    firmware: arm_scmi: Fix double free in SMC transport cleanup path
> 
>   drivers/firmware/arm_scmi/smc.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
Acked-by: Tim Gardner <tim.gardner at canonical.com>
-- 
-----------
Tim Gardner
Canonical, Inc