From: Fredrik Strupe fredrik@strupe.net
commit fc2266011accd5aeb8ebc335c381991f20e26e33 upstream.
For thumb instructions, call_undef_hook() in traps.c first reads a u16, and if the u16 indicates a T32 instruction (u16 >= 0xe800), a second u16 is read, which then makes up the the lower half-word of a T32 instruction. For T16 instructions, the second u16 is not read, which makes the resulting u32 opcode always have the upper half set to 0.
However, having the upper half of instr_mask in the undef_hook set to 0 masks out the upper half of all thumb instructions - both T16 and T32. This results in trapped T32 instructions with the lower half-word equal to the T16 encoding of setend (b650) being matched, even though the upper half-word is not 0000 and thus indicates a T32 opcode.
An example of such a T32 instruction is eaa0b650, which should raise a SIGILL since T32 instructions with an eaa prefix are unallocated as per Arm ARM, but instead works as a SETEND because the second half-word is set to b650.
This patch fixes the issue by extending instr_mask to include the upper u32 half, which will still match T16 instructions where the upper half is 0, but not T32 instructions.
Fixes: 2d888f48e056 ("arm64: Emulate SETEND for AArch32 tasks") Cc: stable@vger.kernel.org # 4.0.x- Reviewed-by: Suzuki K Poulose suzuki.poulose@arm.com Signed-off-by: Fredrik Strupe fredrik@strupe.net Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arm64/kernel/armv8_deprecated.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/arm64/kernel/armv8_deprecated.c +++ b/arch/arm64/kernel/armv8_deprecated.c @@ -607,7 +607,7 @@ static struct undef_hook setend_hooks[] }, { /* Thumb mode */ - .instr_mask = 0x0000fff7, + .instr_mask = 0xfffffff7, .instr_val = 0x0000b650, .pstate_mask = (COMPAT_PSR_T_BIT | COMPAT_PSR_MODE_MASK), .pstate_val = (COMPAT_PSR_T_BIT | COMPAT_PSR_MODE_USR),