lib/generic-radix-tree.c: Fix rare race in __genradix_ptr_alloc()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: lib/generic-radix-tree.c: Fix rare race in __genradix_ptr_alloc() If we need to increase the tree depth, allocate a new node, and then race with another thread that increased the tree depth before us, we'll still have a preallocated node that might be used later. If we then use that node for a new non-root node, it'll still have a pointer to the old root instead of being zeroed - fix this by zeroing it in the cmpxchg failure path.

References

• https://git.kernel.org/stable/c/0f27f4f445390cb7f73d4209cb2bf32834dc53da
• https://git.kernel.org/stable/c/99418ec776a39609f50934720419e0b464ca2283
• https://git.kernel.org/stable/c/ad5ee9feebc2eb8cfc76ed74a2d6e55343b0e169
• https://git.kernel.org/stable/c/ebeff038744c498a036e7a92eb8e433ae0a386d7
• https://git.kernel.org/stable/c/d942e855324a60107025c116245095632476613e
• https://git.kernel.org/stable/c/0f078f8ca93b28a34e20bd050f12cd4efeee7c0f
• https://git.kernel.org/stable/c/b2f11c6f3e1fc60742673b8675c95b78447f3dae