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Subject[PATCH 2/3] x86/uprobes: Fix not using prefixes.nbytes for loop over prefixes.bytes
Date
Since the insn.prefixes.nbytes can be bigger than the size of
insn.prefixes.bytes[] when a same prefix is repeated, we have to
check whether the insn.prefixes.bytes[i] != 0 and i < 4 instead
of insn.prefixes.nbytes.

Fixes: 2b1444983508 ("uprobes, mm, x86: Add the ability to install and remove uprobes breakpoints")
Cc: stable@vger.kernel.org
Reported-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
arch/x86/kernel/uprobes.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 3fdaa042823d..bb3ea3705b99 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -257,7 +257,7 @@ static bool is_prefix_bad(struct insn *insn)
{
int i;

- for (i = 0; i < insn->prefixes.nbytes; i++) {
+ for (i = 0; insn->prefixes.bytes[i] && i < 4; i++) {
insn_attr_t attr;

attr = inat_get_opcode_attribute(insn->prefixes.bytes[i]);
@@ -746,7 +746,7 @@ static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
* Intel and AMD behavior differ in 64-bit mode: Intel ignores 66 prefix.
* No one uses these insns, reject any branch insns with such prefix.
*/
- for (i = 0; i < insn->prefixes.nbytes; i++) {
+ for (i = 0; insn->prefixes.bytes[i] && i < 4; i++) {
if (insn->prefixes.bytes[i] == 0x66)
return -ENOTSUPP;
}
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