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

[Bethany Jamison]

[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(+)

-- 
2.34.1