CVE-2023-53468

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

ubifs: Fix memory leak in alloc_wbufs()

kmemleak reported a sequence of memory leaks, and show them as following:

unreferenced object 0xffff8881575f8400 (size 1024): comm mount, pid 19625, jiffies 4297119604 (age 20.383s) 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: [] __kmalloc+0x4d/0x150 [] ubifs_mount+0x307b/0x7170 [ubifs] [] legacy_get_tree+0xed/0x1d0 [] vfs_get_tree+0x7d/0x230 [] path_mount+0xdd4/0x17b0 [] __x64_sys_mount+0x1fa/0x270 [] do_syscall_64+0x35/0x80 [] entry_SYSCALL_64_after_hwframe+0x46/0xb0

unreferenced object 0xffff8881798a6e00 (size 512): comm mount, pid 19677, jiffies 4297121912 (age 37.816s) hex dump (first 32 bytes): 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk backtrace: [] __kmalloc+0x4d/0x150 [] ubifs_wbuf_init+0x52/0x480 [ubifs] [] ubifs_mount+0x31f5/0x7170 [ubifs] [] legacy_get_tree+0xed/0x1d0 [] vfs_get_tree+0x7d/0x230 [] path_mount+0xdd4/0x17b0 [] __x64_sys_mount+0x1fa/0x270 [] do_syscall_64+0x35/0x80 [] entry_SYSCALL_64_after_hwframe+0x46/0xb0

The problem is that the ubifs_wbuf_init() returns an error in the loop which in the alloc_wbufs(), then the wbuf->buf and wbuf->inodes that were successfully alloced before are not freed.

Fix it by adding error hanging path in alloc_wbufs() which frees the memory alloced before when ubifs_wbuf_init() returns an error.

Weakness

The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.

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/1f206002c6bc302bface871ef3f72c0bbcaa931c
• https://git.kernel.org/stable/c/26ec45f1c504e15268383019df139d7983f1e67f
• https://git.kernel.org/stable/c/3e29634eb56e6547272fe4e568f63421f8b3b9fa
• https://git.kernel.org/stable/c/4a1ff3c5d04b9079b4f768d9a71b51c4af578dd2
• https://git.kernel.org/stable/c/bf50229494f0443b3f08427d7df63e5a7e2a796a
• https://git.kernel.org/stable/c/e11f36d3bc4d23f620754a948fe7b82b63dcb185