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Commit0d07c0e

Browse files
mhiramatsuryasaimadhu
authored andcommitted
x86/kprobes: Fix optprobe to detect INT3 padding correctly
Commit7705dc8 ("x86/vmlinux: Use INT3 instead of NOP for linker fill bytes")changed the padding bytes between functions from NOP to INT3. However,when optprobe decodes a target function it finds INT3 and gives up thejump optimization.Instead of giving up any INT3 detection, check whether the rest of thebytes to the end of the function are INT3. If all of them are INT3,those come from the linker. In that case, continue the optprobe jumpoptimization. [ bp: Massage commit message. ]Fixes:7705dc8 ("x86/vmlinux: Use INT3 instead of NOP for linker fill bytes")Reported-by: Adam Zabrocki <pi3@pi3.com.pl>Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>Signed-off-by: Borislav Petkov <bp@suse.de>Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>Reviewed-by: Kees Cook <keescook@chromium.org>Cc: stable@vger.kernel.orgLink:https://lkml.kernel.org/r/160767025681.3880685.16021570341428835411.stgit@devnote2
1 parent190113b commit0d07c0e

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1 file changed

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  • arch/x86/kernel/kprobes

1 file changed

+20
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‎arch/x86/kernel/kprobes/opt.c‎

Lines changed: 20 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -272,6 +272,19 @@ static int insn_is_indirect_jump(struct insn *insn)
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returnret;
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}
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staticboolis_padding_int3(unsigned longaddr,unsigned longeaddr)
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{
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unsignedcharops;
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for (;addr<eaddr;addr++) {
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if (get_kernel_nofault(ops, (void*)addr)<0||
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ops!=INT3_INSN_OPCODE)
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return false;
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}
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return true;
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}
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/* Decode whole function to ensure any instructions don't jump into target */
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staticintcan_optimize(unsigned longpaddr)
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{
@@ -310,9 +323,14 @@ static int can_optimize(unsigned long paddr)
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return0;
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kernel_insn_init(&insn, (void*)recovered_insn,MAX_INSN_SIZE);
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insn_get_length(&insn);
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/* Another subsystem puts a breakpoint */
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/*
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* In the case of detecting unknown breakpoint, this could be
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* a padding INT3 between functions. Let's check that all the
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* rest of the bytes are also INT3.
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*/
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if (insn.opcode.bytes[0]==INT3_INSN_OPCODE)
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return0;
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returnis_padding_int3(addr,paddr-offset+size) ?1 :0;
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/* Recover address */
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insn.kaddr= (void*)addr;
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insn.next_byte= (void*)(addr+insn.length);

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