git: c6ccb08686f3 - main - ibcore: Fix a use-after-free in ucma_resolve_ip().

[Hans Petter Selasky]

The branch main has been updated by hselasky:

URL: https://cgit.FreeBSD.org/src/commit/?id=c6ccb08686f3b92c12778b4b903431b2ce71ec2c

commit c6ccb08686f3b92c12778b4b903431b2ce71ec2c
Author:     Hans Petter Selasky <hselasky at FreeBSD.org>
AuthorDate: 2021-06-16 13:01:47 +0000
Commit:     Hans Petter Selasky <hselasky at FreeBSD.org>
CommitDate: 2021-07-12 12:22:32 +0000

    ibcore: Fix a use-after-free in ucma_resolve_ip().
    
    There is a race condition between ucma_close() and ucma_resolve_ip():
    
    CPU0                            CPU1
    ucma_resolve_ip():              ucma_close():
    
    ctx = ucma_get_ctx(file, cmd.id);
    
            list_for_each_entry_safe(ctx, tmp, &file->ctx_list, list) {
                    mutex_lock(&mut);
                    idr_remove(&ctx_idr, ctx->id);
                    mutex_unlock(&mut);
                    ...
                    mutex_lock(&mut);
                    if (!ctx->closing) {
                            mutex_unlock(&mut);
                            rdma_destroy_id(ctx->cm_id);
                    ...
                    ucma_free_ctx(ctx);
            }
    
    ret = rdma_resolve_addr();
    ucma_put_ctx(ctx);
    
    Before idr_remove(), ucma_get_ctx() could still find the ctx
    and after rdma_destroy_id(), rdma_resolve_addr() may still
    access id_priv pointer. Also, ucma_put_ctx() may use ctx after
    ucma_free_ctx() too.
    
    ucma_close() should call ucma_put_ctx() too which tests the
    refcnt and waits for the last one releasing it. The similar
    pattern is already used by ucma_destroy_id().
    
    Linux commit:
    5fe23f262e0548ca7f19fb79f89059a60d087d22
    
    MFC after:      1 week
    Reviewed by:    kib
    Sponsored by:   Mellanox Technologies // NVIDIA Networking
---
 sys/ofed/drivers/infiniband/core/ib_ucma.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sys/ofed/drivers/infiniband/core/ib_ucma.c b/sys/ofed/drivers/infiniband/core/ib_ucma.c
index 19e4a17836ee..878e4d348234 100644
--- a/sys/ofed/drivers/infiniband/core/ib_ucma.c
+++ b/sys/ofed/drivers/infiniband/core/ib_ucma.c
@@ -1705,6 +1705,8 @@ static int ucma_close(struct inode *inode, struct file *filp)
 		mutex_lock(&mut);
 		if (!ctx->closing) {
 			mutex_unlock(&mut);
+			ucma_put_ctx(ctx);
+			wait_for_completion(&ctx->comp);
 			/* rdma_destroy_id ensures that no event handlers are
 			 * inflight for that id before releasing it.
 			 */