CVE-2021-47328

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

scsi: iscsi: Fix conn use after free during resets

If we havent done a unbind target call we can race where iscsi_conn_teardown wakes up the EH thread and then frees the conn while those threads are still accessing the conn ehwait.

We can only do one TMF per session so this just moves the TMF fields from the conn to the session. We can then rely on the iscsi_session_teardown->iscsi_remove_session->__iscsi_unbind_session call to remove the target and its devices, and know after that point there is no device or scsi-ml callout trying to access the session.

Weakness

Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.

Affected Software

Extended Description

The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:

In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.

Potential Mitigations

References

• https://git.kernel.org/stable/c/89812e7957ab0746eab66ed6fc49d52bb4dca250
• https://git.kernel.org/stable/c/bf20d85a88384574fabb3d53ad62a8af57e7ab11
• https://git.kernel.org/stable/c/d04958a348e560938410e04a12fb99da9c7e6a00
• https://git.kernel.org/stable/c/ec29d0ac29be366450a7faffbcf8cba3a6a3b506
• https://git.kernel.org/stable/c/f0a031f7c55ffd944fead1ddaf2aa94df9a158c1
• https://git.kernel.org/stable/c/fa9542b35ceb4202e8f8d65f440529a63524dca9
• https://git.kernel.org/stable/c/89812e7957ab0746eab66ed6fc49d52bb4dca250
• https://git.kernel.org/stable/c/bf20d85a88384574fabb3d53ad62a8af57e7ab11
• https://git.kernel.org/stable/c/d04958a348e560938410e04a12fb99da9c7e6a00
• https://git.kernel.org/stable/c/ec29d0ac29be366450a7faffbcf8cba3a6a3b506
• https://git.kernel.org/stable/c/f0a031f7c55ffd944fead1ddaf2aa94df9a158c1
• https://git.kernel.org/stable/c/fa9542b35ceb4202e8f8d65f440529a63524dca9