From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 08E4226F288; Thu, 12 Mar 2026 20:26:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773347166; cv=none; b=RGqq3pBJFZClympCWL7RtsaRlsv72LET0mP+A9aGC09N+AVz0oiNinWgi9XHxFtvVj8LqbqyYz0dW3CddtySvMC+GhD+Nbv96f5GMLSb0vp1GcIZQDcQdDBqFuH0+UFDMVvlC6fTVwiW6lEl2gfdUV4XdZ81Z3lGlnmkwneHPiM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773347166; c=relaxed/simple; bh=ce8Euzm4YIY0c1JCRVYrsN9dPt/z9qXeji5qz4VxZYQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=eRCzcGXrhNjtjpUJcyKRf8crsFLQ/XsjwDl/ZjJgt22/H0xudAdkww+xpYAMYdrepH8YwvKUmjQjjqgGdP6DMGopgc1DY7wIRPQfa3iK7FQGZaoMGoAN7wwEFEqWePBXbUcxxHbfB38fbRknz1tFTQVGPs9AyZ5e7fKt/awm1bg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=p7ejCTfD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="p7ejCTfD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5F807C4CEF7; Thu, 12 Mar 2026 20:26:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1773347165; bh=ce8Euzm4YIY0c1JCRVYrsN9dPt/z9qXeji5qz4VxZYQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=p7ejCTfDnoDMs7VH3UJnkLREFh7eYl/fP4obL/uS8kaYlTnVRblRSe0RnOoJAjClO tGaq826wXxeUZ+4RBGnDNmtiANMaSceB+yttnzU45FV6m3iBUujZv5IAlVFehnEWxu 8NfI/d6YbZtsNwjbf8aZ0KYIagmbIIRZO/L9/PO4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Charles Haithcock , Wolfram Sang , Sasha Levin Subject: [PATCH 6.12 221/265] i2c: i801: Revert "i2c: i801: replace acpi_lock with I2C bus lock" Date: Thu, 12 Mar 2026 21:10:08 +0100 Message-ID: <20260312201026.306243096@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260312201018.128816016@linuxfoundation.org> References: <20260312201018.128816016@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Charles Haithcock [ Upstream commit cfc69c2e6c699c96949f7b0455195b0bfb7dc715 ] This reverts commit f707d6b9e7c18f669adfdb443906d46cfbaaa0c1. Under rare circumstances, multiple udev threads can collect i801 device info on boot and walk i801_acpi_io_handler somewhat concurrently. The first will note the area is reserved by acpi to prevent further touches. This ultimately causes the area to be deregistered. The second will enter i801_acpi_io_handler after the area is unregistered but before a check can be made that the area is unregistered. i2c_lock_bus relies on the now unregistered area containing lock_ops to lock the bus. The end result is a kernel panic on boot with the following backtrace; [ 14.971872] ioatdma 0000:09:00.2: enabling device (0100 -> 0102) [ 14.971873] BUG: kernel NULL pointer dereference, address: 0000000000000000 [ 14.971880] #PF: supervisor read access in kernel mode [ 14.971884] #PF: error_code(0x0000) - not-present page [ 14.971887] PGD 0 P4D 0 [ 14.971894] Oops: 0000 [#1] PREEMPT SMP PTI [ 14.971900] CPU: 5 PID: 956 Comm: systemd-udevd Not tainted 5.14.0-611.5.1.el9_7.x86_64 #1 [ 14.971905] Hardware name: XXXXXXXXXXXXXXXXXXXXXXX BIOS 1.20.10.SV91 01/30/2023 [ 14.971908] RIP: 0010:i801_acpi_io_handler+0x2d/0xb0 [i2c_i801] [ 14.971929] Code: 00 00 49 8b 40 20 41 57 41 56 4d 8b b8 30 04 00 00 49 89 ce 41 55 41 89 d5 41 54 49 89 f4 be 02 00 00 00 55 4c 89 c5 53 89 fb <48> 8b 00 4c 89 c7 e8 18 61 54 e9 80 bd 80 04 00 00 00 75 09 4c 3b [ 14.971933] RSP: 0018:ffffbaa841483838 EFLAGS: 00010282 [ 14.971938] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff9685e01ba568 [ 14.971941] RDX: 0000000000000008 RSI: 0000000000000002 RDI: 0000000000000000 [ 14.971944] RBP: ffff9685ca22f028 R08: ffff9685ca22f028 R09: ffff9685ca22f028 [ 14.971948] R10: 000000000000000b R11: 0000000000000580 R12: 0000000000000580 [ 14.971951] R13: 0000000000000008 R14: ffff9685e01ba568 R15: ffff9685c222f000 [ 14.971954] FS: 00007f8287c0ab40(0000) GS:ffff96a47f940000(0000) knlGS:0000000000000000 [ 14.971959] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 14.971963] CR2: 0000000000000000 CR3: 0000000168090001 CR4: 00000000003706f0 [ 14.971966] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 14.971968] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 14.971972] Call Trace: [ 14.971977] [ 14.971981] ? show_trace_log_lvl+0x1c4/0x2df [ 14.971994] ? show_trace_log_lvl+0x1c4/0x2df [ 14.972003] ? acpi_ev_address_space_dispatch+0x16e/0x3c0 [ 14.972014] ? __die_body.cold+0x8/0xd [ 14.972021] ? page_fault_oops+0x132/0x170 [ 14.972028] ? exc_page_fault+0x61/0x150 [ 14.972036] ? asm_exc_page_fault+0x22/0x30 [ 14.972045] ? i801_acpi_io_handler+0x2d/0xb0 [i2c_i801] [ 14.972061] acpi_ev_address_space_dispatch+0x16e/0x3c0 [ 14.972069] ? __pfx_i801_acpi_io_handler+0x10/0x10 [i2c_i801] [ 14.972085] acpi_ex_access_region+0x5b/0xd0 [ 14.972093] acpi_ex_field_datum_io+0x73/0x2e0 [ 14.972100] acpi_ex_read_data_from_field+0x8e/0x230 [ 14.972106] acpi_ex_resolve_node_to_value+0x23d/0x310 [ 14.972114] acpi_ds_evaluate_name_path+0xad/0x110 [ 14.972121] acpi_ds_exec_end_op+0x321/0x510 [ 14.972127] acpi_ps_parse_loop+0xf7/0x680 [ 14.972136] acpi_ps_parse_aml+0x17a/0x3d0 [ 14.972143] acpi_ps_execute_method+0x137/0x270 [ 14.972150] acpi_ns_evaluate+0x1f4/0x2e0 [ 14.972158] acpi_evaluate_object+0x134/0x2f0 [ 14.972164] acpi_evaluate_integer+0x50/0xe0 [ 14.972173] ? vsnprintf+0x24b/0x570 [ 14.972181] acpi_ac_get_state.part.0+0x23/0x70 [ 14.972189] get_ac_property+0x4e/0x60 [ 14.972195] power_supply_show_property+0x90/0x1f0 [ 14.972205] add_prop_uevent+0x29/0x90 [ 14.972213] power_supply_uevent+0x109/0x1d0 [ 14.972222] dev_uevent+0x10e/0x2f0 [ 14.972228] uevent_show+0x8e/0x100 [ 14.972236] dev_attr_show+0x19/0x40 [ 14.972246] sysfs_kf_seq_show+0x9b/0x100 [ 14.972253] seq_read_iter+0x120/0x4b0 [ 14.972262] ? selinux_file_permission+0x106/0x150 [ 14.972273] vfs_read+0x24f/0x3a0 [ 14.972284] ksys_read+0x5f/0xe0 [ 14.972291] do_syscall_64+0x5f/0xe0 ... The kernel panic is mitigated by setting limiting the count of udev children to 1. Revert to using the acpi_lock to continue protecting marking the area as owned by firmware without relying on a lock in a potentially unmapped region of memory. Fixes: f707d6b9e7c1 ("i2c: i801: replace acpi_lock with I2C bus lock") Signed-off-by: Charles Haithcock [wsa: added Fixes-tag and updated comment stating the importance of the lock] Signed-off-by: Wolfram Sang Signed-off-by: Sasha Levin --- drivers/i2c/busses/i2c-i801.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c index be7ca6a0ebeb8..24363acfc3f8c 100644 --- a/drivers/i2c/busses/i2c-i801.c +++ b/drivers/i2c/busses/i2c-i801.c @@ -303,9 +303,10 @@ struct i801_priv { /* * If set to true the host controller registers are reserved for - * ACPI AML use. + * ACPI AML use. Needs extra protection by acpi_lock. */ bool acpi_reserved; + struct mutex acpi_lock; }; #define FEATURE_SMBUS_PEC BIT(0) @@ -893,8 +894,11 @@ static s32 i801_access(struct i2c_adapter *adap, u16 addr, int hwpec, ret; struct i801_priv *priv = i2c_get_adapdata(adap); - if (priv->acpi_reserved) + mutex_lock(&priv->acpi_lock); + if (priv->acpi_reserved) { + mutex_unlock(&priv->acpi_lock); return -EBUSY; + } pm_runtime_get_sync(&priv->pci_dev->dev); @@ -935,6 +939,7 @@ static s32 i801_access(struct i2c_adapter *adap, u16 addr, pm_runtime_mark_last_busy(&priv->pci_dev->dev); pm_runtime_put_autosuspend(&priv->pci_dev->dev); + mutex_unlock(&priv->acpi_lock); return ret; } @@ -1586,7 +1591,7 @@ i801_acpi_io_handler(u32 function, acpi_physical_address address, u32 bits, * further access from the driver itself. This device is now owned * by the system firmware. */ - i2c_lock_bus(&priv->adapter, I2C_LOCK_SEGMENT); + mutex_lock(&priv->acpi_lock); if (!priv->acpi_reserved && i801_acpi_is_smbus_ioport(priv, address)) { priv->acpi_reserved = true; @@ -1606,7 +1611,7 @@ i801_acpi_io_handler(u32 function, acpi_physical_address address, u32 bits, else status = acpi_os_write_port(address, (u32)*value, bits); - i2c_unlock_bus(&priv->adapter, I2C_LOCK_SEGMENT); + mutex_unlock(&priv->acpi_lock); return status; } @@ -1666,6 +1671,7 @@ static int i801_probe(struct pci_dev *dev, const struct pci_device_id *id) priv->adapter.dev.parent = &dev->dev; acpi_use_parent_companion(&priv->adapter.dev); priv->adapter.retries = 3; + mutex_init(&priv->acpi_lock); priv->pci_dev = dev; priv->features = id->driver_data; -- 2.51.0