[PATCH 5.16 049/126] RDMA/ucma: Protect mc during concurrent multicast leaves

Greg Kroah-Hartman
2022-02-07T12:00:19Z

From: Leon Romanovsky <leonro@nvidia.com>

commit 36e8169ec973359f671f9ec7213547059cae972e upstream.

Partially revert the commit mentioned in the Fixes line to make sure that
allocation and erasing multicast struct are locked.

BUG: KASAN: use-after-free in ucma_cleanup_multicast drivers/infiniband/core/ucma.c:491 [inline]
BUG: KASAN: use-after-free in ucma_destroy_private_ctx+0x914/0xb70 drivers/infiniband/core/ucma.c:579
Read of size 8 at addr ffff88801bb74b00 by task syz-executor.1/25529
CPU: 0 PID: 25529 Comm: syz-executor.1 Not tainted 5.16.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_address_description.constprop.0.cold+0x8d/0x320 mm/kasan/report.c:247
__kasan_report mm/kasan/report.c:433 [inline]
kasan_report.cold+0x83/0xdf mm/kasan/report.c:450
ucma_cleanup_multicast drivers/infiniband/core/ucma.c:491 [inline]
ucma_destroy_private_ctx+0x914/0xb70 drivers/infiniband/core/ucma.c:579
ucma_destroy_id+0x1e6/0x280 drivers/infiniband/core/ucma.c:614
ucma_write+0x25c/0x350 drivers/infiniband/core/ucma.c:1732
vfs_write+0x28e/0xae0 fs/read_write.c:588
ksys_write+0x1ee/0x250 fs/read_write.c:643
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

Currently the xarray search can touch a concurrently freeing mc as the
xa_for_each() is not surrounded by any lock. Rather than hold the lock for
a full scan hold it only for the effected items, which is usually an empty
list.

Fixes: 95fe51096b7a ("RDMA/ucma: Remove mc_list and rely on xarray")
Link: https://lore.kernel.org/r/1cda5fabb1081e8d16e39a48d3a4f8160cea88b8.1642491047.git.leonro@nvidia.com
Reported-by: syzbot+e3f96c43d19782dd14a7@syzkaller.appspotmail.com
Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Maor Gottlieb <maorg@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/infiniband/core/ucma.c | 34 +++++++++++++++++++++++-----------
1 file changed, 23 insertions(+), 11 deletions(-)

--- a/drivers/infiniband/core/ucma.c
+++ b/drivers/infiniband/core/ucma.c
@@ -95,6 +95,7 @@ struct ucma_context {
u64 uid;

struct list_head list;
+ struct list_head mc_list;
struct work_struct close_work;
};

@@ -105,6 +106,7 @@ struct ucma_multicast {

u64 uid;
u8 join_state;
+ struct list_head list;
struct sockaddr_storage addr;
};

@@ -198,6 +200,7 @@ static struct ucma_context *ucma_alloc_c

INIT_WORK(&ctx->close_work, ucma_close_id);
init_completion(&ctx->comp);
+ INIT_LIST_HEAD(&ctx->mc_list);
/* So list_del() will work if we don't do ucma_finish_ctx() */
INIT_LIST_HEAD(&ctx->list);
ctx->file = file;
@@ -484,19 +487,19 @@ err1:

static void ucma_cleanup_multicast(struct ucma_context *ctx)
{
- struct ucma_multicast *mc;
- unsigned long index;
+ struct ucma_multicast *mc, *tmp;

- xa_for_each(&multicast_table, index, mc) {
- if (mc->ctx != ctx)
- continue;
+ xa_lock(&multicast_table);
+ list_for_each_entry_safe(mc, tmp, &ctx->mc_list, list) {
+ list_del(&mc->list);
/*
* At this point mc->ctx->ref is 0 so the mc cannot leave the
* lock on the reader and this is enough serialization
*/
- xa_erase(&multicast_table, index);
+ __xa_erase(&multicast_table, mc->id);
kfree(mc);
}
+ xa_unlock(&multicast_table);
}

static void ucma_cleanup_mc_events(struct ucma_multicast *mc)
@@ -1469,12 +1472,16 @@ static ssize_t ucma_process_join(struct
mc->uid = cmd->uid;
memcpy(&mc->addr, addr, cmd->addr_size);

- if (xa_alloc(&multicast_table, &mc->id, NULL, xa_limit_32b,
+ xa_lock(&multicast_table);
+ if (__xa_alloc(&multicast_table, &mc->id, NULL, xa_limit_32b,
GFP_KERNEL)) {
ret = -ENOMEM;
goto err_free_mc;
}

+ list_add_tail(&mc->list, &ctx->mc_list);
+ xa_unlock(&multicast_table);
+
mutex_lock(&ctx->mutex);
ret = rdma_join_multicast(ctx->cm_id, (struct sockaddr *)&mc->addr,
join_state, mc);
@@ -1500,8 +1507,11 @@ err_leave_multicast:
mutex_unlock(&ctx->mutex);
ucma_cleanup_mc_events(mc);
err_xa_erase:
- xa_erase(&multicast_table, mc->id);
+ xa_lock(&multicast_table);
+ list_del(&mc->list);
+ __xa_erase(&multicast_table, mc->id);
err_free_mc:
+ xa_unlock(&multicast_table);
kfree(mc);
err_put_ctx:
ucma_put_ctx(ctx);
@@ -1569,15 +1579,17 @@ static ssize_t ucma_leave_multicast(stru
mc = ERR_PTR(-EINVAL);
else if (!refcount_inc_not_zero(&mc->ctx->ref))
mc = ERR_PTR(-ENXIO);
- else
- __xa_erase(&multicast_table, mc->id);
- xa_unlock(&multicast_table);

if (IS_ERR(mc)) {
+ xa_unlock(&multicast_table);
ret = PTR_ERR(mc);
goto out;
}

+ list_del(&mc->list);
+ __xa_erase(&multicast_table, mc->id);
+ xa_unlock(&multicast_table);
+
mutex_lock(&mc->ctx->mutex);
rdma_leave_multicast(mc->ctx->cm_id, (struct sockaddr *) &mc->addr);
mutex_unlock(&mc->ctx->mutex);