Description

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().

Metrics

 

CVSS Version 4.0 CVSS Version 3.x CVSS Version 2.0

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CVSS 4.0 Severity and Vector Strings:

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CVSS 3.x Severity and Vector Strings:

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CVSS 2.0 Severity and Vector Strings:

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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:

kernel.org https://git.kernel.org/stable/c/3c34fb0bd4a4237592c5ecb5b2e2531900c55774 [No types assigned]

kernel.org https://git.kernel.org/stable/c/52100fd74ad07b53a4666feafff1cd11436362d3 [No types assigned]

kernel.org https://git.kernel.org/stable/c/a723a6c8d4831cc8e2c7b0c9f3f0c010d4671964 [No types assigned]

kernel.org https://git.kernel.org/stable/c/f4df9d6c8d4e4c818252b0419c2165d66eabd4eb [No types assigned]