Messages in this thread | | | Subject | Re: [PATCH] ACPI: scan: Fix a Hyper-V Linux VM panic caused by buffer overflow | From | Dwaipayan Ray <> | Date | Thu, 7 Jan 2021 19:09:53 +0530 |
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On 18/12/20 9:38 am, Dexuan Cui wrote: > Linux VM on Hyper-V crashes with the latest mainline: > > [ 4.069624] detected buffer overflow in strcpy > [ 4.077733] kernel BUG at lib/string.c:1149! > .. > [ 4.085819] RIP: 0010:fortify_panic+0xf/0x11 > ... > [ 4.085819] Call Trace: > [ 4.085819] acpi_device_add.cold.15+0xf2/0xfb > [ 4.085819] acpi_add_single_object+0x2a6/0x690 > [ 4.085819] acpi_bus_check_add+0xc6/0x280 > [ 4.085819] acpi_ns_walk_namespace+0xda/0x1aa > [ 4.085819] acpi_walk_namespace+0x9a/0xc2 > [ 4.085819] acpi_bus_scan+0x78/0x90 > [ 4.085819] acpi_scan_init+0xfa/0x248 > [ 4.085819] acpi_init+0x2c1/0x321 > [ 4.085819] do_one_initcall+0x44/0x1d0 > [ 4.085819] kernel_init_freeable+0x1ab/0x1f4 > > This is because of the recent buffer overflow detection in the > commit 6a39e62abbaf ("lib: string.h: detect intra-object overflow in fortified string functions") > > Here acpi_device_bus_id->bus_id can only hold 14 characters, while the > the acpi_device_hid(device) returns a 22-char string > "HYPER_V_GEN_COUNTER_V1". > > Per ACPI Spec v6.2, Section 6.1.5 _HID (Hardware ID), if the ID is a > string, it must be of the form AAA#### or NNNN####, i.e. 7 chars or 8 > chars. > > The field bus_id in struct acpi_device_bus_id was originally defined as > char bus_id[9], and later was enlarged to char bus_id[15] in 2007 in the > commit bb0958544f3c ("ACPI: use more understandable bus_id for ACPI devices") > > It looks like so far an ID string of >=15 chars is only seen in the guest > BIOS/firmware by Hyper-V, and AFAIK the ID string "HYPER_V_GEN_COUNTER_V1" > is never used by Linux VM on Hyper-V, so let's just truncate the string to > fix the panic. > > Signed-off-by: Dexuan Cui <decui@microsoft.com> > --- > drivers/acpi/scan.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c > index a1b226eb2ce2..b801442b6b1b 100644 > --- a/drivers/acpi/scan.c > +++ b/drivers/acpi/scan.c > @@ -674,7 +674,8 @@ int acpi_device_add(struct acpi_device *device, > } > if (!found) { > acpi_device_bus_id = new_bus_id; > - strcpy(acpi_device_bus_id->bus_id, acpi_device_hid(device)); > + strlcpy(acpi_device_bus_id->bus_id, acpi_device_hid(device), > + sizeof(acpi_device_bus_id->bus_id));
Please prefer strscpy() over strlcpy():
+ strscpy(acpi_device_bus_id->bus_id, acpi_device_hid(device), + sizeof(acpi_device_bus_id->bus_id));
See: https://lore.kernel.org/lkml/CAHk-=wgfRnXz0W3D37d01q3JFkr_i_uTL=V6A6G1oUZcprmknw@mail.gmail.com/
Thanks, Dwaipayan.
> acpi_device_bus_id->instance_no = 0; > list_add_tail(&acpi_device_bus_id->node, &acpi_bus_id_list); > }
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