0d1fd39bb2
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@kernel.org Signed-off-by: Leon Romanovsky <leonro@mellanox.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.