CVE-2025-21892

In the Linux kernel, the following vulnerability has been resolved:

RDMA/mlx5: Fix the recovery flow of the UMR QP

This patch addresses an issue in the recovery flow of the UMR QP,

ensuring tasks do not get stuck, as highlighted by the call trace [1].

During recovery, before transitioning the QP to the RESET state, the

software must wait for all outstanding WRs to complete.

Failing to do so can cause the firmware to skip sending some flushed

CQEs with errors and simply discard them upon the RESET, as per the IB

specification.

This race condition can result in lost CQEs and tasks becoming stuck.

To resolve this, the patch sends a final WR which serves only as a

barrier before moving the QP state to RESET.

Once a CQE is received for that final WR, it guarantees that no

outstanding WRs remain, making it safe to transition the QP to RESET and

subsequently back to RTS, restoring proper functionality.

Note:

For the barrier WR, we simply reuse the failed and ready WR.

Since the QP is in an error state, it will only receive

IB_WC_WR_FLUSH_ERR. However, as it serves only as a barrier we don't

care about its status.

[1]

INFO: task rdma_resource_l:1922 blocked for more than 120 seconds.

Tainted: G W 6.12.0-rc7+ #1626

"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:rdma_resource_l state:D stack:0 pid:1922 tgid:1922 ppid:1369

flags:0x00004004

Call Trace:

<TASK>

__schedule+0x420/0xd30

schedule+0x47/0x130

schedule_timeout+0x280/0x300

? mark_held_locks+0x48/0x80

? lockdep_hardirqs_on_prepare+0xe5/0x1a0

wait_for_completion+0x75/0x130

mlx5r_umr_post_send_wait+0x3c2/0x5b0 [mlx5_ib]

? __pfx_mlx5r_umr_done+0x10/0x10 [mlx5_ib]

mlx5r_umr_revoke_mr+0x93/0xc0 [mlx5_ib]

__mlx5_ib_dereg_mr+0x299/0x520 [mlx5_ib]

? _raw_spin_unlock_irq+0x24/0x40

? wait_for_completion+0xfe/0x130

? rdma_restrack_put+0x63/0xe0 [ib_core]

ib_dereg_mr_user+0x5f/0x120 [ib_core]

? lock_release+0xc6/0x280

destroy_hw_idr_uobject+0x1d/0x60 [ib_uverbs]

uverbs_destroy_uobject+0x58/0x1d0 [ib_uverbs]

uobj_destroy+0x3f/0x70 [ib_uverbs]

ib_uverbs_cmd_verbs+0x3e4/0xbb0 [ib_uverbs]

? __pfx_uverbs_destroy_def_handler+0x10/0x10 [ib_uverbs]

? __lock_acquire+0x64e/0x2080

? mark_held_locks+0x48/0x80

? find_held_lock+0x2d/0xa0

? lock_acquire+0xc1/0x2f0

? ib_uverbs_ioctl+0xcb/0x170 [ib_uverbs]

? __fget_files+0xc3/0x1b0

ib_uverbs_ioctl+0xe7/0x170 [ib_uverbs]

? ib_uverbs_ioctl+0xcb/0x170 [ib_uverbs]

__x64_sys_ioctl+0x1b0/0xa70

do_syscall_64+0x6b/0x140

entry_SYSCALL_64_after_hwframe+0x76/0x7e

RIP: 0033:0x7f99c918b17b

RSP: 002b:00007ffc766d0468 EFLAGS: 00000246 ORIG_RAX:

0000000000000010

RAX: ffffffffffffffda RBX: 00007ffc766d0578 RCX:

00007f99c918b17b

RDX: 00007ffc766d0560 RSI: 00000000c0181b01 RDI:

0000000000000003

RBP: 00007ffc766d0540 R08: 00007f99c8f99010 R09:

000000000000bd7e

R10: 00007f99c94c1c70 R11: 0000000000000246 R12:

00007ffc766d0530

R13: 000000000000001c R14: 0000000040246a80 R15:

0000000000000000

</TASK>