nfc: nci: fix out-of-bounds write in nci_target_auto_activated()

Overview

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

nfc: nci: fix out-of-bounds write in nci_target_auto_activated()

nci_target_auto_activated() appends a target to the fixed-size array ndev->targets[NCI_MAX_DISCOVERED_TARGETS] and increments ndev->n_targets without first checking the array is full; unlike its sibling nci_add_new_target(), which bails out when n_targets already equals NCI_MAX_DISCOVERED_TARGETS.

ndev->n_targets is only cleared by nci_clear_target_list(), so an NFCC that repeatedly re-runs discovery (RF_DISCOVER_RSP, which re-enters NCI_DISCOVERY without clearing the target list) and reports an auto-activated target (RF_INTF_ACTIVATED_NTF) drives n_targets past the limit. The append then writes a struct nfc_target past the end of the array (a slab out-of-bounds write), and nfc_targets_found() goes on to walk the array with the inflated count:

BUG: KASAN: slab-out-of-bounds in nci_add_new_protocol+0x94/0x2ac [nci] Write of size 2 at addr ffff0000c7299a18 by task kworker/u8:0/12 Workqueue: nfc0_nci_rx_wq nci_rx_work [nci] Call trace: nci_add_new_protocol+0x94/0x2ac [nci] nci_ntf_packet+0xddc/0x11a0 [nci] nci_rx_work+0x15c/0x1e0 [nci] process_one_work+0x2dc/0x500 worker_thread+0x240/0x460 kthread+0x1c0/0x1d0 ret_from_fork+0x10/0x20

The buggy address belongs to the cache kmalloc-2k of size 2048 The buggy address is located 1024 bytes to the right of allocated 1560-byte region [ffff0000c7299000, ffff0000c7299618)

Guard nci_target_auto_activated() with the same check used by nci_add_new_target().

Affected

• Linux >= 019c4fbaa790e2b3f11dab0c8b7d9896d77db3e5 < 0dc59de0075f88404a0f4a2b5233104ef459fbb2
• Linux >= 019c4fbaa790e2b3f11dab0c8b7d9896d77db3e5 < 94530ffabfca57e9bff1d207106010014cc84032
• Linux >= 019c4fbaa790e2b3f11dab0c8b7d9896d77db3e5 < afd8605fb43becb892311102844955c3b127fc7e
• Linux >= 019c4fbaa790e2b3f11dab0c8b7d9896d77db3e5 < 24761d3a5f692df5f7d848caeabcb2afd10917aa
• Linux >= 019c4fbaa790e2b3f11dab0c8b7d9896d77db3e5 < 50e87e1c0e18d791dcd7dccf30f9a2f3e2cf3951
• Linux >= 019c4fbaa790e2b3f11dab0c8b7d9896d77db3e5 < 2f08dbce3b37624ec6b424d759336a99586170ec
• Linux >= 019c4fbaa790e2b3f11dab0c8b7d9896d77db3e5 < d7083f41c21b30582e91b2e6de4d54dce74f6f9c
• Linux >= 019c4fbaa790e2b3f11dab0c8b7d9896d77db3e5 < 129032c0616d83a5e3e304f6ebf88f14ba01e5f7
• Linux >= 019c4fbaa790e2b3f11dab0c8b7d9896d77db3e5 < ac200079db50af81e6b04d058b33ec92901d8edd
• Linux 3.4

Remediation

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