Regression bisected to "crypto: af_alg: Convert af_alg_sendpage() to use MSG_SPLICE_PAGES"

[Ondrej Mosnáček <omosnacek@xxxxxxxxx>]

Hello,

It seems that the commit:

commit fb800fa4c1f5aee1238267252e88a7837e645c02
Author: David Howells <dhowells@xxxxxxxxxx>
Date:   Tue Jun 6 14:08:55 2023 +0100

   crypto: af_alg: Convert af_alg_sendpage() to use MSG_SPLICE_PAGES

...causes a segfault in libkcapi's test suite. A simplified reproducer:

git clone https://github.com/smuellerDD/libkcapi/
cd libkcapi
autoreconf -i
./configure --enable-kcapi-test
make
./bin/kcapi -x 2 -s  -c "gcm(aes)" -i aac774c39e399e7d6371ec1d \
    -k 38bd9eb2cb29cc42ac38d6cdbe116760 \
    -a 5dbb2884f3fe93664613e863c3bd2572855cf808765880ef1fa5787ceef8c793 \
    -t 34a21cc3562f0ba141d73242e5a3b666 \
    -q d127b39d365d16246d2866b2ebabd201

The last command prints the result and then segfaults in a cleanup
free(3) call. Before the mentioned commit it printed the result and
completed successfully. I haven't dug any deeper to figure out the
root cause.

Cheers,
Ondrej