CVE-2021-46924

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

NFC: st21nfca: Fix memory leak in device probe and remove

phy->pending_skb is alloced when device probe, but forgot to free in the error handling path and remove path, this cause memory leak as follows:

unreferenced object 0xffff88800bc06800 (size 512): comm 8, pid 11775, jiffies 4295159829 (age 9.032s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ……………. 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ……………. backtrace: [<00000000d66c09ce>] __kmalloc_node_track_caller+0x1ed/0x450 [<00000000c93382b3>] kmalloc_reserve+0x37/0xd0 [<000000005fea522c>] __alloc_skb+0x124/0x380 [<0000000019f29f9a>] st21nfca_hci_i2c_probe+0x170/0x8f2

Fix it by freeing pending_skb in error and remove.

Weakness

The product does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory.

Affected Software

Potential Mitigations

• Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone.
• For example, glibc in Linux provides protection against free of invalid pointers.
• When using Xcode to target OS X or iOS, enable automatic reference counting (ARC) [REF-391].
• To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std::auto_ptr (defined by ISO/IEC ISO/IEC 14882:2003), std::shared_ptr and std::unique_ptr (specified by an upcoming revision of the C++ standard, informally referred to as C++ 1x), or equivalent solutions such as Boost.

References

• https://git.kernel.org/stable/c/1b9dadba502234eea7244879b8d5d126bfaf9f0c
• https://git.kernel.org/stable/c/1cd4063dbc91cf7965d73a6a3855e2028cd4613b
• https://git.kernel.org/stable/c/238920381b8925d070d32d73cd9ce52ab29896fe
• https://git.kernel.org/stable/c/38c3e320e7ff46f2dc67bc5045333e63d9f8918d
• https://git.kernel.org/stable/c/a1e0080a35a16ce3808f7040fe0c3a8fdb052349
• https://git.kernel.org/stable/c/e553265ea56482da5700f56319fda9ff53e7dcb4