From: Alexandra Winter wintera@linux.ibm.com

stable inclusion from stable-v4.19.320 commit 84f40b46787ecb67c7ad08a5bb1376141fa10c01 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAKPRZ CVE: CVE-2024-42271

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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[ Upstream commit f558120cd709682b739207b48cf7479fd9568431 ]

iucv_sever_path() is called from process context and from bh context. iucv->path is used as indicator whether somebody else is taking care of severing the path (or it is already removed / never existed). This needs to be done with atomic compare and swap, otherwise there is a small window where iucv_sock_close() will try to work with a path that has already been severed and freed by iucv_callback_connrej() called by iucv_tasklet_fn().

Example: [452744.123844] Call Trace: [452744.123845] ([<0000001e87f03880>] 0x1e87f03880) [452744.123966] [<00000000d593001e>] iucv_path_sever+0x96/0x138 [452744.124330] [<000003ff801ddbca>] iucv_sever_path+0xc2/0xd0 [af_iucv] [452744.124336] [<000003ff801e01b6>] iucv_sock_close+0xa6/0x310 [af_iucv] [452744.124341] [<000003ff801e08cc>] iucv_sock_release+0x3c/0xd0 [af_iucv] [452744.124345] [<00000000d574794e>] __sock_release+0x5e/0xe8 [452744.124815] [<00000000d5747a0c>] sock_close+0x34/0x48 [452744.124820] [<00000000d5421642>] __fput+0xba/0x268 [452744.124826] [<00000000d51b382c>] task_work_run+0xbc/0xf0 [452744.124832] [<00000000d5145710>] do_notify_resume+0x88/0x90 [452744.124841] [<00000000d5978096>] system_call+0xe2/0x2c8 [452744.125319] Last Breaking-Event-Address: [452744.125321] [<00000000d5930018>] iucv_path_sever+0x90/0x138 [452744.125324] [452744.125325] Kernel panic - not syncing: Fatal exception in interrupt

Note that bh_lock_sock() is not serializing the tasklet context against process context, because the check for sock_owned_by_user() and corresponding handling is missing.

Ideas for a future clean-up patch: A) Correct usage of bh_lock_sock() in tasklet context, as described in Link: https://lore.kernel.org/netdev/1280155406.2899.407.camel@edumazet-laptop/ Re-enqueue, if needed. This may require adding return values to the tasklet functions and thus changes to all users of iucv.

B) Change iucv tasklet into worker and use only lock_sock() in af_iucv.

Fixes: 7d316b945352 ("af_iucv: remove IUCV-pathes completely") Reviewed-by: Halil Pasic pasic@linux.ibm.com Signed-off-by: Alexandra Winter wintera@linux.ibm.com Link: https://patch.msgid.link/20240729122818.947756-1-wintera@linux.ibm.com Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Dong Chenchen dongchenchen2@huawei.com --- net/iucv/af_iucv.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/iucv/af_iucv.c b/net/iucv/af_iucv.c index f024914da1b2..6085df9ba561 100644 --- a/net/iucv/af_iucv.c +++ b/net/iucv/af_iucv.c @@ -450,8 +450,8 @@ static void iucv_sever_path(struct sock *sk, int with_user_data) struct iucv_sock *iucv = iucv_sk(sk); struct iucv_path *path = iucv->path;

- if (iucv->path) { - iucv->path = NULL; + /* Whoever resets the path pointer, must sever and free it. */ + if (xchg(&iucv->path, NULL)) { if (with_user_data) { low_nmcpy(user_data, iucv->src_name); high_nmcpy(user_data, iucv->dst_name);