UBUNTU-CVE-2024-40910
In the Linux kernel, the following vulnerability has been resolved: ax25: Fix refcount imbalance on inbound connections When releasing a socket in ax25_release(), we call netdev_put() to decrease the refcount on the associated ax.25 device. However, the execution path for accepting an incoming connection never calls netdev_hold(). This imbalance leads to refcount errors, and ultimately to kernel crashes. A typical call trace for the above situation will start with one of the following errors: refcount_t: decrement hit 0; leaking memory. refcount_t: underflow; use-after-free. And will then have a trace like: Call Trace: <TASK> ? show_regs+0x64/0x70 ? __warn+0x83/0x120 ? refcount_warn_saturate+0xb2/0x100 ? report_bug+0x158/0x190 ? prb_read_valid+0x20/0x30 ? handle_bug+0x3e/0x70 ? exc_invalid_op+0x1c/0x70 ? asm_exc_invalid_op+0x1f/0x30 ? refcount_warn_saturate+0xb2/0x100 ? refcount_warn_saturate+0xb2/0x100 ax25_release+0x2ad/0x360 __sock_release+0x35/0xa0 sock_close+0x19/0x20 [...] On reboot (or any attempt to remove the interface), the kernel gets stuck in an infinite loop: unregister_netdevice: waiting for ax0 to become free. Usage count = 0 This patch corrects these issues by ensuring that we call netdev_hold() and ax25_dev_hold() for new connections in ax25_accept(). This makes the logic leading to ax25_accept() match the logic for ax25_bind(): in both cases we increment the refcount, which is ultimately decremented in ax25_release().
02 / AFFECTED SOFTWARE
Affected packages
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03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
In the Linux kernel, the following vulnerability has been resolved: ax25: Fix refcount imbalance on inbound connections When releasing a socket in ax25_release(), we call netdev_put() to decrease the refcount on the associated ax.25 device. However, the execution path for accepting an incoming connection never calls netdev_hold(). This imbalance leads to refcount errors, and ultimately to kernel crashes. A typical call trace for the above situation will start with one of the following errors: refcount_t: decrement hit 0; leaking memory. refcount_t: underflow; use-after-free. And will then have a trace like: Call Trace: <TASK> ? show_regs+0x64/0x70 ? __warn+0x83/0x120 ? refcount_warn_saturate+0xb2/0x100 ? report_bug+0x158/0x190 ? prb_read_valid+0x20/0x30 ? handle_bug+0x3e/0x70 ? exc_invalid_op+0x1c/0x70 ? asm_exc_invalid_op+0x1f/0x30 ? refcount_warn_saturate+0xb2/0x100 ? refcount_warn_saturate+0xb2/0x100 ax25_release+0x2ad/0x360 __sock_release+0x35/0xa0 sock_close+0x19/0x20 [...] On reboot (or any attempt to remove the interface), the kernel gets stuck in an infinite loop: unregister_netdevice: waiting for ax0 to become free. Usage count = 0 This patch corrects these issues by ensuring that we call netdev_hold() and ax25_dev_hold() for new connections in ax25_accept(). This makes the logic leading to ax25_accept() match the logic for ax25_bind(): in both cases we increment the refcount, which is ultimately decremented in ax25_release().
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/3c34fb0bd4a4237592c5ecb5b2e2531900c55774
- https://ubuntu.com/security/CVE-2024-40910
- https://ubuntu.com/security/notices/USN-6999-1
- https://ubuntu.com/security/notices/USN-6999-2
- https://ubuntu.com/security/notices/USN-7004-1
- https://ubuntu.com/security/notices/USN-7005-1
- https://ubuntu.com/security/notices/USN-7005-2
- https://ubuntu.com/security/notices/USN-7008-1
- https://ubuntu.com/security/notices/USN-7029-1
- https://ubuntu.com/security/notices/USN-7173-1
- https://ubuntu.com/security/notices/USN-7173-2
- https://ubuntu.com/security/notices/USN-7173-3
- https://ubuntu.com/security/notices/USN-7179-1
- https://ubuntu.com/security/notices/USN-7179-2
- https://ubuntu.com/security/notices/USN-7179-3
- https://ubuntu.com/security/notices/USN-7179-4
- https://ubuntu.com/security/notices/USN-7186-1
- https://ubuntu.com/security/notices/USN-7186-2
- https://ubuntu.com/security/notices/USN-7194-1
- https://ubuntu.com/security/notices/USN-7195-1
- https://ubuntu.com/security/notices/USN-7195-2
- https://ubuntu.com/security/notices/USN-7332-1
- https://ubuntu.com/security/notices/USN-7332-2
- https://ubuntu.com/security/notices/USN-7332-3
- https://ubuntu.com/security/notices/USN-7342-1
- https://ubuntu.com/security/notices/USN-7344-1
- https://ubuntu.com/security/notices/USN-7344-2
- https://ubuntu.com/security/notices/USN-7413-1
- https://www.cve.org/CVERecord?id=CVE-2024-40910