50 lines
1.8 KiB
Diff
50 lines
1.8 KiB
Diff
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From eefdca043e8391dcd719711716492063030b55ac Mon Sep 17 00:00:00 2001
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From: Roland McGrath <roland@redhat.com>
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Date: Tue, 14 Sep 2010 12:22:58 -0700
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Subject: [PATCH] x86-64, compat: Retruncate rax after ia32 syscall entry tracing
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In commit d4d6715, we reopened an old hole for a 64-bit ptracer touching a
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32-bit tracee in system call entry. A %rax value set via ptrace at the
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entry tracing stop gets used whole as a 32-bit syscall number, while we
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only check the low 32 bits for validity.
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Fix it by truncating %rax back to 32 bits after syscall_trace_enter,
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in addition to testing the full 64 bits as has already been added.
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Reported-by: Ben Hawkes <hawkes@sota.gen.nz>
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Signed-off-by: Roland McGrath <roland@redhat.com>
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Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
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---
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arch/x86/ia32/ia32entry.S | 8 +++++++-
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1 files changed, 7 insertions(+), 1 deletions(-)
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diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
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index 84e3a4e..518bb99 100644
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--- a/arch/x86/ia32/ia32entry.S
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+++ b/arch/x86/ia32/ia32entry.S
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@@ -50,7 +50,12 @@
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/*
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* Reload arg registers from stack in case ptrace changed them.
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* We don't reload %eax because syscall_trace_enter() returned
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- * the value it wants us to use in the table lookup.
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+ * the %rax value we should see. Instead, we just truncate that
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+ * value to 32 bits again as we did on entry from user mode.
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+ * If it's a new value set by user_regset during entry tracing,
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+ * this matches the normal truncation of the user-mode value.
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+ * If it's -1 to make us punt the syscall, then (u32)-1 is still
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+ * an appropriately invalid value.
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*/
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.macro LOAD_ARGS32 offset, _r9=0
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.if \_r9
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@@ -60,6 +65,7 @@
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movl \offset+48(%rsp),%edx
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movl \offset+56(%rsp),%esi
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movl \offset+64(%rsp),%edi
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+ movl %eax,%eax /* zero extension */
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.endm
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.macro CFI_STARTPROC32 simple
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--
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1.7.2.3
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