From: Leon Romanovsky <leonro@xxxxxxxxxxxx>
[ Upstream commit 0d1fd39bb27e479fb1de3dd4b4c247c7c9a1fabf ]
The FD should not be installed until all of the setup is completed as the
fd_install() transfers ownership of the kref to the FD table. A thread can
race a close() and trigger concurrent rdma_alloc_commit_uobject() and
uverbs_uobject_fd_release() which, at least, triggers a safety WARN_ON:
WARNING: CPU: 4 PID: 6913 at drivers/infiniband/core/rdma_core.c:768 uverbs_uobject_fd_release+0x202/0x230
Kernel panic - not syncing: panic_on_warn set ...
CPU: 4 PID: 6913 Comm: syz-executor.3 Not tainted 5.7.0-rc2 #22
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014
[..]
RIP: 0010:uverbs_uobject_fd_release+0x202/0x230
Code: fe 4c 89 e7 e8 af 23 fe ff e9 2a ff ff ff e8 c5 fa 61 fe be 03 00 00 00 4c 89 e7 e8 68 eb f5 fe e9 13 ff ff ff e8 ae fa 61 fe <0f> 0b eb ac e8 e5 aa 3c fe e8 50 2b 86 fe e9 6a fe ff ff e8 46 2b
RSP: 0018:ffffc90008117d88 EFLAGS: 00010293
RAX: ffff88810e146580 RBX: 1ffff92001022fb1 RCX: ffffffff82d5b902
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff88811951b040
RBP: ffff88811951b000 R08: ffffed10232a3609 R09: ffffed10232a3609
R10: ffff88811951b043 R11: 0000000000000001 R12: ffff888100a7c600
R13: ffff888100a7c650 R14: ffffc90008117da8 R15: ffffffff82d5b700
? __uverbs_cleanup_ufile+0x270/0x270
? uverbs_uobject_fd_release+0x202/0x230
? uverbs_uobject_fd_release+0x202/0x230
? __uverbs_cleanup_ufile+0x270/0x270
? locks_remove_file+0x282/0x3d0
? security_file_free+0xaa/0xd0
__fput+0x2be/0x770
task_work_run+0x10e/0x1b0
exit_to_usermode_loop+0x145/0x170
do_syscall_64+0x2d0/0x390
? prepare_exit_to_usermode+0x17a/0x230
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x414da7
Code: 00 00 0f 05 48 3d 00 f0 ff ff 77 3f f3 c3 0f 1f 44 00 00 53 89 fb 48 83 ec 10 e8 f4 fb ff ff 89 df 89 c2 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 2b 89 d7 89 44 24 0c e8 36 fc ff ff 8b 44 24
RSP: 002b:00007fff39d379d0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000414da7
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000003
RBP: 00007fff39d37a3c R08: 0000000400000000 R09: 0000000400000000
R10: 00007fff39d37910 R11: 0000000000000293 R12: 0000000000000001
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000003
Reorder so that fd_install() is the last thing done in
rdma_alloc_commit_uobject().
Fixes: aba94548c9e4 ("IB/uverbs: Move the FD uobj type struct file allocation to alloc_commit")
Link: https://lore.kernel.org/r/20200716102059.1420681-1-leon@xxxxxxxxxx
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/infiniband/core/rdma_core.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/infiniband/core/rdma_core.c b/drivers/infiniband/core/rdma_core.c
index 75bcbc625616e..3ab84fcbaadec 100644
--- a/drivers/infiniband/core/rdma_core.c
+++ b/drivers/infiniband/core/rdma_core.c
@@ -638,9 +638,6 @@ void rdma_alloc_commit_uobject(struct ib_uobject *uobj,
{
struct ib_uverbs_file *ufile = attrs->ufile;
- /* alloc_commit consumes the uobj kref */
- uobj->uapi_object->type_class->alloc_commit(uobj);
-
/* kref is held so long as the uobj is on the uobj list. */
uverbs_uobject_get(uobj);
spin_lock_irq(&ufile->uobjects_lock);
@@ -650,6 +647,9 @@ void rdma_alloc_commit_uobject(struct ib_uobject *uobj,
/* matches atomic_set(-1) in alloc_uobj */
atomic_set(&uobj->usecnt, 0);
+ /* alloc_commit consumes the uobj kref */
+ uobj->uapi_object->type_class->alloc_commit(uobj);
+
/* Matches the down_read in rdma_alloc_begin_uobject */
up_read(&ufile->hw_destroy_rwsem);
}
--
2.25.1
