CVE-2021-46956

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

virtiofs: fix memory leak in virtio_fs_probe()

When accidentally passing twice the same tag to qemu, kmemleak ended up reporting a memory leak in virtiofs. Also, looking at the log I saw the following error (thats when I realised the duplicated tag):

virtiofs: probe of virtio5 failed with error -17

Heres the kmemleak log for reference:

unreferenced object 0xffff888103d47800 (size 1024): comm systemd-udevd, pid 118, jiffies 4294893780 (age 18.340s) hex dump (first 32 bytes): 00 00 00 00 ad 4e ad de ff ff ff ff 00 00 00 00 …..N………. ff ff ff ff ff ff ff ff 80 90 02 a0 ff ff ff ff ……………. backtrace: [<000000000ebb87c1>] virtio_fs_probe+0x171/0x7ae [virtiofs] [<00000000f8aca419>] virtio_dev_probe+0x15f/0x210 [<000000004d6baf3c>] really_probe+0xea/0x430 [<00000000a6ceeac8>] device_driver_attach+0xa8/0xb0 [<00000000196f47a7>] __driver_attach+0x98/0x140 [<000000000b20601d>] bus_for_each_dev+0x7b/0xc0 [<00000000399c7b7f>] bus_add_driver+0x11b/0x1f0 [<0000000032b09ba7>] driver_register+0x8f/0xe0 [<00000000cdd55998>] 0xffffffffa002c013 [<000000000ea196a2>] do_one_initcall+0x64/0x2e0 [<0000000008f727ce>] do_init_module+0x5c/0x260 [<000000003cdedab6>] __do_sys_finit_module+0xb5/0x120 [<00000000ad2f48c6>] do_syscall_64+0x33/0x40 [<00000000809526b5>] entry_SYSCALL_64_after_hwframe+0x44/0xae

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/310efc95c72c13faf855c692d19cd4d054d827c8
• https://git.kernel.org/stable/c/5116e79fc6e6725b8acdad8b7e928a83ab7b47e6
• https://git.kernel.org/stable/c/9b9d60c0eb8ada99cce2a9ab5c15dffc523b01ae
• https://git.kernel.org/stable/c/c79c5e0178922a9e092ec8fed026750f39dcaef4
• https://git.kernel.org/stable/c/d19555ff225d0896a33246a49279e6d578095f15
• https://git.kernel.org/stable/c/310efc95c72c13faf855c692d19cd4d054d827c8
• https://git.kernel.org/stable/c/5116e79fc6e6725b8acdad8b7e928a83ab7b47e6
• https://git.kernel.org/stable/c/9b9d60c0eb8ada99cce2a9ab5c15dffc523b01ae
• https://git.kernel.org/stable/c/c79c5e0178922a9e092ec8fed026750f39dcaef4
• https://git.kernel.org/stable/c/d19555ff225d0896a33246a49279e6d578095f15