Executive brief
The Linux kernel's Allwinner Security System (sun8i-ss) hardware random number generator contained a use-after-free vulnerability in its DMA-based PRNG implementation. When a signal interrupted the random number generation process, the driver would fail to properly shut down DMA operations, leading to memory corruption. This patch removes the vulnerable PRNG support entirely as the interface is redundant with other kernel RNG mechanisms.
Technical details
The vulnerability is a use-after-free in the sun8i-ss PRNG driver's ->generate() function, which used wait_for_completion_interruptible_timeout() without properly handling signal delivery and associated DMA shutdown. Additionally, a buffer overread existed in a memcpy() call that read beyond allocated bounds ('memcpy(ctx->seed, d + dlen, ctx->slen)'). The fix removes the entire crypto_rng interface implementation from the driver, including ~250 lines of PRNG code, since the interface is being phased out kernel-wide and redundant with hwrng and the Linux RNG subsystem. The code was accessible only through the kernel cryptographic API and affected systems that explicitly enabled CONFIG_CRYPTO_DEV_SUN8I_SS_PRNG.
Affected products
- Linux Linux kernel versions with sun8i-ss PRNG support (likely 5.x–7.x)
Timeline
- 2026-09-04: disclosed: Published via NVD
- 2026-06-15: patched: Patch authored by Eric Biggers; committed upstream and backported to stable
- 2026-06-15: other: Original vulnerable code introduced by commit ac2614d721de ('crypto: sun8i-ss - Add support for the PRNG')