CVE: CVE-2024-47709
Published: 2024-10-21
Description: In the Linux kernel, the following vulnerability has been resolved:

can: bcm: Clear bo->bcm_proc_read after remove_proc_entry().

syzbot reported a warning in bcm_release(). [0]

The blamed change fixed another warning that is triggered when
connect() is issued again for a socket whose connect()ed device has
been unregistered.

However, if the socket is just close()d without the 2nd connect(), the
remaining bo->bcm_proc_read triggers unnecessary remove_proc_entry()
in bcm_release().

Let's clear bo->bcm_proc_read after remove_proc_entry() in bcm_notify().

[0]
name '4986'
WARNING: CPU: 0 PID: 5234 at fs/proc/generic.c:711 remove_proc_entry+0x2e7/0x5d0 fs/proc/generic.c:711
Modules linked in:
CPU: 0 UID: 0 PID: 5234 Comm: syz-executor606 Not tainted 6.11.0-rc5-syzkaller-00178-g5517ae241919 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
RIP: 0010:remove_proc_entry+0x2e7/0x5d0 fs/proc/generic.c:711
Code: ff eb 05 e8 cb 1e 5e ff 48 8b 5c 24 10 48 c7 c7 e0 f7 aa 8e e8 2a 38 8e 09 90 48 c7 c7 60 3a 1b 8c 48 89 de e8 da 42 20 ff 90 <0f> 0b 90 90 48 8b 44 24 18 48 c7 44 24 40 0e 36 e0 45 49 c7 04 07
RSP: 0018:ffffc9000345fa20 EFLAGS: 00010246
RAX: 2a2d0aee2eb64600 RBX: ffff888032f1f548 RCX: ffff888029431e00
RDX: [PII_REDACTED] RSI: [PII_REDACTED] RDI: [PII_REDACTED]
RBP: ffffc9000345fb08 R08: ffffffff8155b2f2 R09: 1ffff[PII_REDACTED]a
R10: dffffc[PII_REDACTED] R11: ffffed101710519b R12: ffff888011d38640
R13: [PII_REDACTED] R14: [PII_REDACTED] R15: dffffc[PII_REDACTED]
FS:  [PII_REDACTED](0000) GS:ffff8880b8800000(0000) knlGS:[PII_REDACTED]
CS:  0010 DS: 0000 ES: 0000 CR0: [PII_REDACTED]
CR2: 00007fcfb52722f0 CR3: 000000000e734000 CR4:[PII_REDACTED]3506f0
DR0: [PII_REDACTED] DR1: [PII_REDACTED] DR2: [PII_REDACTED]
DR3: [PII_REDACTED] DR6: 00000000fffe0ff0 DR7: [PII_REDACTED]
Call Trace:
 <TASK>
 bcm_release+0x250/0x880 net/can/bcm.c:1578
 __sock_release net/socket.c:659 [inline]
 sock_close+0xbc/0x240 net/socket.c:1421
 __fput+0x24a/0x8a0 fs/file_table.c:422
 task_work_run+0x24f/0x310 kernel/task_work.c:228
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0xa2f/0x27f0 kernel/exit.c:882
 do_group_exit+0x207/0x2c0 kernel/exit.c:1031
 __do_sys_exit_group kernel/exit.c:1042 [inline]
 __se_sys_exit_group kernel/exit.c:1040 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1040
 x64_sys_call+0x2634/0x2640 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fcfb51ee969
Code: Unable to access opcode bytes at 0x7fcfb51ee93f.
RSP: 002b:00007ffce0109ca8 EFLAGS: 00000246 ORIG_RAX:[PII_REDACTED]0000e7
RAX: ffffffffffffffda RBX: [PII_REDACTED] RCX: 00007fcfb51ee969
RDX:[PII_REDACTED]00003c RSI:[PII_REDACTED]0000e7 RDI: [PII_REDACTED]
RBP: 00007fcfb526f3b0 R08: ffffffffffffffb8 R09: [PII_REDACTED]
R10: [PII_REDACTED] R11: [PII_REDACTED] R12: 00007fcfb526f3b0
R13: [PII_REDACTED] R14: 00007fcfb5271ee0 R15: 00007fcfb51bf160
 </TASK>
CVSS Score: 5.5 (MEDIUM)
References: https://git.kernel.org/stable/c/5cc00913c1fdcab861c4e65fa20d1f1e1bbbf977; https://git.kernel.org/stable/c/770b463264426cc3c167b1d44efa85f6a526ce5b; https://git.kernel.org/stable/c/7a145d6ec2124bdb94bd6fc436b342ff6ddf2b70