From: Rob Gardner rob.gardner@oracle.com
[ Upstream commit e5e8b80d352ec999d2bba3ea584f541c83f4ca3f ]
is_no_fault_exception() has two bugs which were discovered via random opcode testing with stress-ng. Both are caused by improper filtering of opcodes.
The first bug can be triggered by a floating point store with a no-fault ASI, for instance "sta %f0, [%g0] #ASI_PNF", opcode C1A01040.
The code first tests op3[5] (0x1000000), which denotes a floating point instruction, and then tests op3[2] (0x200000), which denotes a store instruction. But these bits are not mutually exclusive, and the above mentioned opcode has both bits set. The intent is to filter out stores, so the test for stores must be done first in order to have any effect.
The second bug can be triggered by a floating point load with one of the invalid ASI values 0x8e or 0x8f, which pass this check in is_no_fault_exception(): if ((asi & 0xf2) == ASI_PNF)
An example instruction is "ldqa [%l7 + %o7] #ASI 0x8f, %f38", opcode CF95D1EF. Asi values greater than 0x8b (ASI_SNFL) are fatal in handle_ldf_stq(), and is_no_fault_exception() must not allow these invalid asi values to make it that far.
In both of these cases, handle_ldf_stq() reacts by calling sun4v_data_access_exception() or spitfire_data_access_exception(), which call is_no_fault_exception() and results in an infinite recursion.
Signed-off-by: Rob Gardner rob.gardner@oracle.com Tested-by: Anatoly Pugachev matorola@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- arch/sparc/kernel/traps_64.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/arch/sparc/kernel/traps_64.c b/arch/sparc/kernel/traps_64.c index d92e5eaa4c1d..a850dccd78ea 100644 --- a/arch/sparc/kernel/traps_64.c +++ b/arch/sparc/kernel/traps_64.c @@ -275,14 +275,13 @@ bool is_no_fault_exception(struct pt_regs *regs) asi = (regs->tstate >> 24); /* saved %asi */ else asi = (insn >> 5); /* immediate asi */ - if ((asi & 0xf2) == ASI_PNF) { - if (insn & 0x1000000) { /* op3[5:4]=3 */ - handle_ldf_stq(insn, regs); - return true; - } else if (insn & 0x200000) { /* op3[2], stores */ + if ((asi & 0xf6) == ASI_PNF) { + if (insn & 0x200000) /* op3[2], stores */ return false; - } - handle_ld_nf(insn, regs); + if (insn & 0x1000000) /* op3[5:4]=3 (fp) */ + handle_ldf_stq(insn, regs); + else + handle_ld_nf(insn, regs); return true; } }