[PATCH] ucma: fix a use-after-free in ucma_resolve_ip()

[PATCH] ucma: fix a use-after-free in ucma_resolve_ip()

[Cong Wang]

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().

Reported-and-tested-by: syzbot+da2591e115d57a9cbb8b@syzkaller.appspotmail.com
Reported-by: syzbot+cfe3c1e8ef634ba8964b@syzkaller.appspotmail.com
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Doug Ledford <dledford@redhat.com>
Cc: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
---
 drivers/infiniband/core/ucma.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/infiniband/core/ucma.c b/drivers/infiniband/core/ucma.c
index 5f437d1570fb..21863ddde63e 100644
--- a/drivers/infiniband/core/ucma.c
+++ b/drivers/infiniband/core/ucma.c
@@ -1759,6 +1759,8 @@ 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.
 			 */
-- 
2.14.4

Re: [PATCH] ucma: fix a use-after-free in ucma_resolve_ip()

[Leon Romanovsky]

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On Wed, Sep 12, 2018 at 04:27:44PM -0700, Cong Wang wrote:
> 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().
>
> Reported-and-tested-by: syzbot+da2591e115d57a9cbb8b@syzkaller.appspotmail.com
> Reported-by: syzbot+cfe3c1e8ef634ba8964b@syzkaller.appspotmail.com
> Cc: Jason Gunthorpe <jgg@mellanox.com>
> Cc: Doug Ledford <dledford@redhat.com>
> Cc: Leon Romanovsky <leon@kernel.org>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
> ---
>  drivers/infiniband/core/ucma.c | 2 ++
>  1 file changed, 2 insertions(+)
>

Thanks,
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>

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Re: [PATCH] ucma: fix a use-after-free in ucma_resolve_ip()

[Doug Ledford]

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On Wed, 2018-09-12 at 16:27 -0700, Cong Wang wrote:
> 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().
> 
> Reported-and-tested-by: syzbot+da2591e115d57a9cbb8b@syzkaller.appspotmail.com
> Reported-by: syzbot+cfe3c1e8ef634ba8964b@syzkaller.appspotmail.com
> Cc: Jason Gunthorpe <jgg@mellanox.com>
> Cc: Doug Ledford <dledford@redhat.com>
> Cc: Leon Romanovsky <leon@kernel.org>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>

Thanks, applied to for-rc.

-- 
Doug Ledford <dledford@redhat.com>
    GPG KeyID: B826A3330E572FDD
    Key fingerprint = AE6B 1BDA 122B 23B4 265B  1274 B826 A333 0E57 2FDD

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