firewire: ohci: fix NULL pointer dereference in ar_context_release

Overview

In the Linux kernel, the following vulnerability has been resolved:

firewire: ohci: fix NULL pointer dereference in ar_context_release

During the error handling path of the driver's probe function, a NULL pointer dereference can occur in ar_context_release().

When pci_probe() fails early (e.g., if pcim_enable_device() or MMIO mapping fails), the devres cleanup mechanism invokes release_ohci(). This function unconditionally calls ar_context_release() to clean up the asynchronous receive contexts. However, if ar_context_init() was not yet called, ctx->ohci remains NULL (as the fw_ohci structure is zero-initialized by devres_alloc()).

ar_context_release() immediately dereferences ctx->ohci to get the dev pointer before checking if the context was actually initialized, leading to a crash:

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f] RIP: 0010:ar_context_release+0x3f/0x380 drivers/firewire/ohci.c:543 Call Trace: release_ohci+0x3f/0x60 drivers/firewire/ohci.c:3567 release_nodes drivers/base/devres.c:546 [inline] devres_release_all+0x1a8/0x260 drivers/base/devres.c:576 device_unbind_cleanup drivers/base/dd.c:597 [inline] really_probe+0x451/0xae0 drivers/base/dd.c:772

To fix this, move the assignment of the dev pointer after the !ctx->buffer check. If ctx->buffer is NULL, it indicates that the context was never successfully initialized and there is nothing to release, safely avoiding the dereference of the uninitialized ctx->ohci pointer.

Affected

• Linux >= 5716e58aecdd4f7225c2e46ce903a839fc54f22f < 3770a4794a14331c8ca6a674e49c021827521c2c
• Linux >= 5716e58aecdd4f7225c2e46ce903a839fc54f22f < ca2fa74f3200ced6e0a940753ad99844c42ad7c8
• Linux >= 5716e58aecdd4f7225c2e46ce903a839fc54f22f < ed5470771c7ed7f959230c4697f316af83426a90
• Linux >= 5716e58aecdd4f7225c2e46ce903a839fc54f22f < 7d228ba43279de2d191f25e139fad166409c2c06
• Linux >= 5716e58aecdd4f7225c2e46ce903a839fc54f22f < 42d217add8d80d6e7d9f58f80d11ea9b07ea113e
• Linux 6.5

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.