CVE-2023-52632: drm/amdkfd: Fix lock dependency warning with srcu

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

drm/amdkfd: Fix lock dependency warning with srcu

====================================================== WARNING: possible circular locking dependency detected 6.5.0-kfd-yangp #2289 Not tainted ------------------------------------------------------ kworker/0:2/996 is trying to acquire lock: (srcu){.+.+}-{0:0}, at: synchronizesrcu+0x5/0x1a0

but task is already holding lock: ((workcompletion)(&svms->deferredlistwork)){+.+.}-{0:0}, at: processonework+0x211/0x560

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #3 ((workcompletion)(&svms->deferredlistwork)){+.+.}-{0:0}: flushwork+0x88/0x4f0 svmrangelistlockandflushwork+0x3d/0x110 [amdgpu] svmrangesetattr+0xd6/0x14c0 [amdgpu] kfdioctl+0x1d1/0x630 [amdgpu] x64sysioctl+0x88/0xc0

-> #2 (&info->lock#2){+.+.}-{3:3}: mutexlock+0x99/0xc70 amdgpuamdkfdgpuvmrestoreprocessbos+0x54/0x740 [amdgpu] restoreprocesshelper+0x22/0x80 [amdgpu] restoreprocessworker+0x2d/0xa0 [amdgpu] processonework+0x29b/0x560 workerthread+0x3d/0x3d0

-> #1 ((workcompletion)(&(&process->restorework)->work)){+.+.}-{0:0}: flushwork+0x88/0x4f0 cancelworktimer+0x12c/0x1c0 kfdprocessnotifierreleaseinternal+0x37/0x1f0 [amdgpu] mmunotifierrelease+0xad/0x240 exitmmap+0x6a/0x3a0 mmput+0x6a/0x120 doexit+0x322/0xb90 dogroupexit+0x37/0xa0 x64sysexitgroup+0x18/0x20 dosyscall64+0x38/0x80

-> #0 (srcu){.+.+}-{0:0}: lockacquire+0x1521/0x2510 locksync+0x5f/0x90 synchronizesrcu+0x4f/0x1a0 mmunotifierrelease+0x128/0x240 exitmmap+0x6a/0x3a0 mmput+0x6a/0x120 svmrangedeferredlistwork+0x19f/0x350 [amdgpu] processonework+0x29b/0x560 workerthread+0x3d/0x3d0

other info that might help us debug this: Chain exists of: srcu --> &info->lock#2 --> (workcompletion)(&svms->deferredlistwork)

Possible unsafe locking scenario:

CPU0 CPU1 ---- ---- lock((workcompletion)(&svms->deferredlistwork)); lock(&info->lock#2); lock((workcompletion)(&svms->deferredlistwork)); sync(srcu);