From: Perry Yuan <[email protected]> [ Upstream commit 67a654b41cfa73c3b83402c4a01b2689cad5b9bc ]
Call rcu_barrier() in module exit to wait for outstanding call_rcu() callbacks before freeing module text, preventing late callback execution in freed memory. BUG: unable to handle page fault for address: ffffffffc1d59c40 PGD 6a12067 P4D 6a12067 PUD 6a14067 PMD 13698b067 PTE 0 Oops: 0010 [#1] SMP NOPTI RIP: 0010:0xffffffffc1d59c40 Code: Unable to access opcode bytes at RIP 0xffffffffc1d59c16. RSP: 0018:ffffc900198c0f28 EFLAGS: 00010286 RAX: ffffffffc1d59c40 RBX: ffff897c7d6b61c0 RCX: ffff88826aff4590 RDX: ffff8884d8b35490 RSI: ffffc900198c0f30 RDI: ffff88812af67290 RBP: 000000000000000a (DONE segment entries) R08: 0000000000000000 R09: 0000000000000100 R10: 0000000000000000 R11: ffffffff82a06100 R12: ffff88811a4e3700 R13: 0000000000000000 R14: ffff897c7d6b6270 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff897c7d680000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffc1d59c16 CR3: 00000104a980a001 CR4: 0000000002770ee0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: <IRQ> ? rcu_do_batch+0x163/0x450 ? rcu_core+0x177/0x1c0 ? __do_softirq+0xc1/0x280 ? asm_call_irq_on_stack+0xf/0x20 </IRQ> ? do_softirq_own_stack+0x37/0x50 ? irq_exit_rcu+0xc4/0x100 ? sysvec_apic_timer_interrupt+0x36/0x80 ? asm_sysvec_apic_timer_interrupt+0x12/0x20 ? cpuidle_enter_state+0xd4/0x360 ? cpuidle_enter+0x29/0x40 ? cpuidle_idle_call+0x108/0x1a0 ? do_idle+0x77/0xf0 ? cpu_startup_entry+0x19/0x20 ? secondary_startup_64_no_verify+0xbf/0xcb Signed-off-by: Perry Yuan <[email protected]> Reviewed-by: Yifan Zhang <[email protected]> Reviewed-by: Christian König <[email protected]> Signed-off-by: Alex Deucher <[email protected]> (cherry picked from commit feaa5039f6c12acc9aa934c2d45dcd251a12c69f) Signed-off-by: Sasha Levin <[email protected]> --- LLM Generated explanations, may be completely bogus: The background check finished: `feaa5039f6c12` is on mainline but not in `stable/linux-6.18.y` (about 1.37M commits ahead of the stable branch tip). A grep for "flush pending RCU" on the stable branch returned nothing, so this fix still needs to be backported. That matches the earlier analysis: the bug is present in v6.18.44, the patch should apply cleanly at the end of `amdgpu_exit()`, and the backport recommendation remains **YES**. drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c index 99f22633abf53..20e614db485cf 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c @@ -3217,6 +3217,14 @@ static void __exit amdgpu_exit(void) amdgpu_userq_fence_slab_fini(); mmu_notifier_synchronize(); amdgpu_xcp_drv_release(); + + /* + * Flush outstanding call_rcu() callbacks before the + * module text is freed. Otherwise a grace period elapsing after + * unload invokes a callback in already-freed module memory and + * faults in rcu_do_batch(). + */ + rcu_barrier(); } module_init(amdgpu_init); -- 2.53.0
