# CVE-2024-26893: linux: In the Linux kernel, the following vulnerability has been resolved:  firmware: arm_scmi: Fix double free in SMC trans...

CVE-2024-26893 is fixed in linux on 1 platform, first by DEBIAN-CVE-2024-26893, released April 17, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2024-26893
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0023
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 17, 2024

## Description

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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.85-1 | [DEBIAN-CVE-2024-26893](https://patchblox.com/security/data/fix/linux/debian-cve-2024-26893.md) | Apr 17, 2024 |
| Linux | linux Debian 13.5 (trixie) | 6.7.12-1 | [DEBIAN-CVE-2024-26893](https://patchblox.com/security/data/fix/linux/debian-cve-2024-26893.md) | Apr 17, 2024 |
| Linux | linux Debian 14 | 6.7.12-1 | [DEBIAN-CVE-2024-26893](https://patchblox.com/security/data/fix/linux/debian-cve-2024-26893.md) | Apr 17, 2024 |

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