CVE-2024-46740

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

binder: fix UAF caused by offsets overwrite

Binder objects are processed and copied individually into the target buffer during transactions. Any raw data in-between these objects is copied as well. However, this raw data copy lacks an out-of-bounds check. If the raw data exceeds the data section size then the copy overwrites the offsets section. This eventually triggers an error that attempts to unwind the processed objects. However, at this point the offsets used to index these objects are now corrupted.

Unwinding with corrupted offsets can result in decrements of arbitrary nodes and lead to their premature release. Other users of such nodes are left with a dangling pointer triggering a use-after-free. This issue is made evident by the following KASAN report (trimmed):

================================================================== BUG: KASAN: slab-use-after-free in rawspin_lock+0xe4/0x19c Write of size 4 at addr ffff47fc91598f04 by task binder-util/743

CPU: 9 UID: 0 PID: 743 Comm: binder-util Not tainted 6.11.0-rc4 #1 Hardware name: linux,dummy-virt (DT) Call trace: rawspinlock+0xe4/0x19c binderfreebuf+0x128/0x434 binderthreadwrite+0x8a4/0x3260 binderioctl+0x18f0/0x258c [...]

Allocated by task 743: __kmalloccachenoprof+0x110/0x270 bindernewnode+0x50/0x700 bindertransaction+0x413c/0x6da8 binderthreadwrite+0x978/0x3260 binderioctl+0x18f0/0x258c [...]

Freed by task 745: kfree+0xbc/0x208 binderthreadread+0x1c5c/0x37d4 binder_ioctl+0x16d8/0x258c [...] ==================================================================

To avoid this issue, let's check that the raw data copy is within the boundaries of the data section.