Description

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

parisc: Fix double SIGFPE crash

Camm noticed that on parisc a SIGFPE exception will crash an application with
a second SIGFPE in the signal handler. Dave analyzed it, and it happens
because glibc uses a double-word floating-point store to atomically update
function descriptors. As a result of lazy binding, we hit a floating-point
store in fpe_func almost immediately.

When the T bit is set, an assist exception trap occurs when when the
co-processor encounters *any* floating-point instruction except for a double
store of register %fr0. The latter cancels all pending traps. Let's fix this
by clearing the Trap (T) bit in the FP status register before returning to the
signal handler in userspace.

The issue can be reproduced with this test program:

root@parisc:~# cat fpe.c

static void fpe_func(int sig, siginfo_t *i, void *v) {
sigset_t set;
sigemptyset(&set);
sigaddset(&set, SIGFPE);
sigprocmask(SIG_UNBLOCK, &set, NULL);
printf("GOT signal %d with si_code %ld\n", sig, i->si_code);
}

int main() {
struct sigaction action = {
.sa_sigaction = fpe_func,
.sa_flags = SA_RESTART|SA_SIGINFO };
sigaction(SIGFPE, &action, 0);
feenableexcept(FE_OVERFLOW);
return printf("%lf\n",1.7976931348623158E308*1.7976931348623158E308);
}

root@parisc:~# gcc fpe.c -lm
root@parisc:~# ./a.out
Floating point exception

root@pa...

Classification

CVE ID: CVE-2025-37991

Affected Products

Vendor: Linux

Product: Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.06% (probability of being exploited)

EPSS Percentile: 17.55% (scored less or equal to compared to others)

EPSS Date: 2025-06-18 (when was this score calculated)

References

https://nvd.nist.gov/vuln/detail/CVE-2025-37991
https://git.kernel.org/stable/c/ec4584495868bd465fe60a3f771915c0e7ce7951
https://git.kernel.org/stable/c/6c639af49e9e5615a8395981eaf5943fb40acd6f
https://git.kernel.org/stable/c/6a098c51d18ec99485668da44294565c43dbc106
https://git.kernel.org/stable/c/cf21e890f56b7d0038ddaf25224e4f4c69ecd143
https://git.kernel.org/stable/c/df3592e493d7f29bae4ffde9a9325de50ddf962e
https://git.kernel.org/stable/c/de3629baf5a33af1919dec7136d643b0662e85ef

Timeline