CVE-2024-46771 — can: bcm: Remove proc entry when dev is unregistered.

Affected: Linux

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

can: bcm: Remove proc entry when dev is unregistered.

syzkaller reported a warning in bcm_connect() below. [0]

The repro calls connect() to vxcan1, removes vxcan1, and calls connect() with ifindex == 0.

Calling connect() for a BCM socket allocates a proc entry. Then, bcm_sk(sk)->bound is set to 1 to prevent further connect().

However, removing the bound device resets bcm_sk(sk)->bound to 0 in bcm_notify().

The 2nd connect() tries to allocate a proc entry with the same name and sets NULL to bcm_sk(sk)->bcm_proc_read, leaking the original proc entry.

Since the proc entry is available only for connect()ed sockets, let's clean up the entry when the bound netdev is unregistered.

[0]: proc_dir_entry 'can-bcm/2456' already registered WARNING: CPU: 1 PID: 394 at fs/proc/generic.c:376 proc_register+0x645/0x8f0 fs/proc/generic.c:375 Modules linked in: CPU: 1 PID: 394 Comm: syz-executor403 Not tainted 6.10.0-rc7-g852e42cc2dd4 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 RIP: 0010:proc_register+0x645/0x8f0 fs/proc/generic.c:375 Code: 00 00 00 00 00 48 85 ed 0f 85 97 02 00 00 4d 85 f6 0f 85 9f 02 00 00 48 c7 c7 9b cb cf 87 48 89 de 4c 89 fa e8 1c 6f eb fe 90 <0f> 0b 90 90 48 c7 c7 98 37 99 89 e8 cb 7e 22 05 bb 00 00 00 10 48 RSP: 0018:ffa0000000cd7c30 EFLAGS: 00010246 RAX: 9e129be1950f0200 RBX: ff1100011b51582c RCX: ff1100011857cd80 RDX: 00000…

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CVE-2024-46771 — can: bcm: Remove proc entry when dev is unregistered.