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ACPICA: Avoid sequence overread in call to strncmp()

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[ Upstream commit 64b9dfd077 ]

ACPICA commit 8b83a8d88dfec59ea147fad35fc6deea8859c58c

ap_get_table_length() checks if tables are valid by
calling ap_is_valid_header(). The latter then calls
ACPI_VALIDATE_RSDP_SIG(Table->Signature).

ap_is_valid_header() accepts struct acpi_table_header as an argument, so
the signature size is always fixed to 4 bytes.

The problem is when the string comparison is between ACPI-defined table
signature and ACPI_SIG_RSDP. Common ACPI table header specifies the
Signature field to be 4 bytes long[1], with the exception of the RSDP
structure whose signature is 8 bytes long "RSD PTR " (including the
trailing blank character)[2]. Calling strncmp(sig, rsdp_sig, 8) would
then result in a sequence overread[3] as sig would be smaller (4 bytes)
than the specified bound (8 bytes).

As a workaround, pass the bound conditionally based on the size of the
signature being passed.

Link: https://uefi.org/specs/ACPI/6.5_A/05_ACPI_Software_Programming_Model.html#system-description-table-header [1]
Link: https://uefi.org/specs/ACPI/6.5_A/05_ACPI_Software_Programming_Model.html#root-system-description-pointer-rsdp-structure [2]
Link: https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wstringop-overread [3]
Link: https://github.com/acpica/acpica/commit/8b83a8d8
Signed-off-by: Ahmed Salem <x0rw3ll@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://patch.msgid.link/2248233.Mh6RI2rZIc@rjwysocki.net
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Ahmed Salem 2025-04-25 21:30:27 +02:00 committed by Greg Kroah-Hartman
parent 106a648780
commit 6448774d58
1 changed files with 1 additions and 1 deletions
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2
include/acpi/actypes.h
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@ -524,7 +524,7 @@ typedef u64 acpi_integer;
/* Support for the special RSDP signature (8 characters) */
#define ACPI_VALIDATE_RSDP_SIG(a) (!strncmp (ACPI_CAST_PTR (char, (a)), ACPI_SIG_RSDP, 8))
#define ACPI_VALIDATE_RSDP_SIG(a) (!strncmp (ACPI_CAST_PTR (char, (a)), ACPI_SIG_RSDP, (sizeof(a) < 8) ? ACPI_NAMESEG_SIZE : 8))
#define ACPI_MAKE_RSDP_SIG(dest) (memcpy (ACPI_CAST_PTR (char, (dest)), ACPI_SIG_RSDP, 8))
/* Support for OEMx signature (x can be any character) */