7.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Muhammad Bilal [ Upstream commit 540b8ae192afb5566c1b13b6884aee87107a26b9 ] hp_calculate_security_buffer() special-cases an empty authentication string and returns a fixed 4 bytes (sizeof(u16) * 2). But hp_populate_security_buffer() does not special-case that same input: for any authentication string that does not start with BEAM_PREFIX, including the empty string, it always builds "UTF_PREFIX + authentication" and converts the result to UTF-16, writing a 2-byte length header plus 2 bytes per character of "" (9 characters), 20 bytes total, regardless of how long "authentication" itself is. The caller, hp_set_attribute(), sizes its kmalloc() buffer using hp_calculate_security_buffer()'s return value, so for an empty authentication token it allocates 4 bytes for the security area but hp_populate_security_buffer() then writes 20 bytes into it, causing a 16-byte heap buffer overflow. The authentication token used here is the current admin/setup password, which is an empty string by default until one is configured. Any write to a writable BIOS attribute while no admin password has been set reaches this path. Fix by removing the special-case early return for an empty string in hp_calculate_security_buffer(). The generic calculation that follows already accounts for the UTF_PREFIX correctly, which naturally yields the same 20 bytes that hp_populate_security_buffer() writes for an empty string, avoiding duplicate logic for special cases. Fixes: b2715aa2e135 ("platform/x86: hp-bioscfg: spmobj-attributes") Reported-by: Josh Snyder Closes: https://lore.kernel.org/platform-driver-x86/20260402-hp-bioscfg-overflow-v1-1-6985f8c9e67c@code406.com/ Cc: stable@vger.kernel.org Signed-off-by: Muhammad Bilal Link: https://patch.msgid.link/20260919060037.84602-1-meatuni001@gmail.com Reviewed-by: Ilpo Järvinen Signed-off-by: Ilpo Järvinen Signed-off-by: Sasha Levin --- drivers/platform/x86/hp/hp-bioscfg/spmobj-attributes.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/drivers/platform/x86/hp/hp-bioscfg/spmobj-attributes.c b/drivers/platform/x86/hp/hp-bioscfg/spmobj-attributes.c index 4d94e48c1a4c8..abf8ce20fe15c 100644 --- a/drivers/platform/x86/hp/hp-bioscfg/spmobj-attributes.c +++ b/drivers/platform/x86/hp/hp-bioscfg/spmobj-attributes.c @@ -47,9 +47,6 @@ size_t hp_calculate_security_buffer(const char *authentication) return sizeof(u16) * 2; authlen = strlen(authentication); - if (!authlen) - return sizeof(u16) * 2; - size = sizeof(u16) + authlen * sizeof(u16); if (!strstarts(authentication, BEAM_PREFIX)) size += strlen(UTF_PREFIX) * sizeof(u16); -- 2.53.0