CVE-2026-98201

Summary

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

Input: zero ff_effect before compat copy in input_ff_effect_from_user

In the compat path input_ff_effect_from_user() aliases the caller's native struct ff_effect with the smaller struct ff_effect_compat and copies only the compat sized prefix:

compat_effect = (struct ff_effect_compat *)effect;

if (copy_from_user(compat_effect, buffer,
		   sizeof(struct ff_effect_compat)))

The tail of the native structure is never written. Callers pass an uninitialized on-stack object, for example evdev_do_ioctl() for EVIOCSFF, so those bytes keep their previous stack contents. input_ff_upload() then stores the full native structure in ff->effects[id], from where a uinput based force feedback daemon can read it back via UI_BEGIN_FF_UPLOAD, disclosing kernel stack memory to userspace.

Zero the effect before the compat copy.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/ed0905fda39682d3da7937184397d3276abbffa8
• https://git.kernel.org/stable/c/ec174c2ab1abb76b20fa167c6db848c3d97aa838
• https://git.kernel.org/stable/c/6c26681c5668c973bd0e951407d670ac60d9cd66
• https://git.kernel.org/stable/c/c5e573bb095d502be7cbbaa99c26a20984111c6d
• https://git.kernel.org/stable/c/b878720e8bcaa4cf7163a5081f904dd6baf11b2c
• https://git.kernel.org/stable/c/0d05b43b55d4784a42ce8fb318175f8ad7d9af5a
• https://git.kernel.org/stable/c/ed0406e490f48ed180df140fe2a81be26bccb1a9
• https://git.kernel.org/stable/c/f84819ef8d66931ee3998fee3c4f03230f4cb6cc

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