sctp: copy zeroed stats to user in sctp_getsockopt_pr_streamstatus() when !streamoute

When an SCTP stream output extension structure (streamoute) has not yet
been allocated, sctp_getsockopt_pr_streamstatus() sets the local stack
variables params.sprstat_abandoned_unsent = 0 and
params.sprstat_abandoned_sent = 0, but then immediately jumps to 'out:',
bypassing copy_to_user(). As a result, when an uninitialized user buffer
is passed to getsockopt(SCTP_PR_STREAM_STATUS), the kernel returns
success (0) without copying the zeroed stats back to user space, leaving
uninitialized data in the user buffer.

Refactor the !streamoute check into an if-else chain so that when
streamoute is NULL, params is zeroed and falls through to copy_to_user(),
copying the zeroed stats to user space and setting retval = 0 once before
returning.

Tested in QEMU against Linux 7.3.0-rc3 using an uninitialized
sctp_prstatus user struct passed to getsockopt(SCTP_PR_STREAM_STATUS) on a
freshly created stream: on the unfixed kernel the user struct contains
uninitialized stack garbage; whereas with this fix applied, getsockopt()
copies zeroed stats into user space and returns 0.

Cc: stable@vger.kernel.org
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Hui Peng <benquike@gmail.com>
Fixes: f952be79cebd ("sctp: introduce struct sctp_stream_out_ext")
Link: https://patch.msgid.link/20260930044611.204739-1-benquike@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions