CVE-2025-40210

Summary

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

Revert "NFSD: Remove the cap on number of operations per NFSv4 COMPOUND"

I've found that pynfs COMP6 now leaves the connection or lease in a strange state, which causes CLOSE9 to hang indefinitely. I've dug into it a little, but I haven't been able to root-cause it yet. However, I bisected to commit 48aab1606fa8 ("NFSD: Remove the cap on number of operations per NFSv4 COMPOUND").

Tianshuo Han also reports a potential vulnerability when decoding an NFSv4 COMPOUND. An attacker can place an arbitrarily large op count in the COMPOUND header, which results in:

[ 51.410584] nfsd: vmalloc error: size 1209533382144, exceeds total pages, mode:0xdc0(GFP_KERNEL|__GFP_ZERO), nodemask=(null),cpuset=/,mems_allowed=0

when NFSD attempts to allocate the COMPOUND op array.

Let's restore the operation-per-COMPOUND limit, but increased to 200 for now.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/b3ee7ce432289deac87b9d14e01f2fe6958f7f0b
• https://git.kernel.org/stable/c/3e7f011c255582d7c914133785bbba1990441713

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