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nop: Fix off-by-one in unmap check (#960)

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This commit is contained in:
Grazfather
2023-07-13 18:30:49 -07:00
committed by GitHub
parent 74e862628a
commit ca7418c912
2 changed files with 24 additions and 10 deletions
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gef.py
+2 -2
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@@ -6030,9 +6030,9 @@ class NopCommand(GenericCommand):
if total_bytes % len(nop):
warn(f"Patching {total_bytes} bytes at {address:#x} will result in a partially patched instruction and may break disassembly")
nops = bytearray(nop * (total_bytes // len(nop)))
end_address = Address(value=address + total_bytes)
end_address = Address(value=address + total_bytes - 1)
if not end_address.valid:
err(f"Cannot patch instruction at {address:#x}: reaching unmapped area")
return
tests/commands/nop.py
+22 -8
View File
@@ -21,7 +21,7 @@ class NopCommand(GefUnitTestGeneric):
@pytest.mark.skipif(ARCH not in ("i686", "x86_64"), reason=f"Skipped for {ARCH}")
def test_cmd_nop_no_arg(self):
res = gdb_start_silent_cmd(
"pi gef.memory.write(gef.arch.pc, p32(0xfeebfeeb))", # 2 short jumps to pc
after=(
@@ -30,12 +30,12 @@ class NopCommand(GefUnitTestGeneric):
)
)
self.assertNoException(res)
self.assertIn(r'\x90\x90\xeb\xfe', res) # 2 nops + 1 short jump
self.assertIn(r"\x90\x90\xeb\xfe", res) # 2 nops + 1 short jump
@pytest.mark.skipif(ARCH not in ("i686", "x86_64"), reason=f"Skipped for {ARCH}")
def test_cmd_nop_arg(self):
res = gdb_start_silent_cmd(
"pi gef.memory.write(gef.arch.sp, p64(0xfeebfeebfeebfeeb))", # 4 short jumps to stack
after=(
@@ -44,7 +44,7 @@ class NopCommand(GefUnitTestGeneric):
)
)
self.assertNoException(res)
self.assertIn(r'\x90\x90\x90\x90\xeb\xfe\xeb\xfe', res) # 4 nops + 2 short jumps
self.assertIn(r"\x90\x90\x90\x90\xeb\xfe\xeb\xfe", res) # 4 nops + 2 short jumps
@pytest.mark.skipif(ARCH not in ("i686", "x86_64"), reason=f"Skipped for {ARCH}")
@@ -63,13 +63,13 @@ class NopCommand(GefUnitTestGeneric):
"pi print(f'*** *pc={u8(gef.memory.read(gef.arch.pc, 1))}')",
after=(
f"{self.cmd} --b",
"pi print(f'*** *pc={u8(gef.memory.read(gef.arch.pc, 1))}')",
"pi print(f'*** *pc={u8(gef.memory.read(gef.arch.pc, 1)):#x}')",
)
)
self.assertNoException(res)
lines = findlines("*** *pc=", res)
self.assertEqual(len(lines), 2)
self.assertEqual(lines[1], "*** *pc=144") # nop -> 0x90 -> 144
self.assertEqual(lines[1], "*** *pc=0x90")
@pytest.mark.skipif(ARCH not in ("i686", "x86_64"), reason=f"Skipped for {ARCH}")
@@ -78,20 +78,34 @@ class NopCommand(GefUnitTestGeneric):
"pi print(f'*** *sp={u32(gef.memory.read(gef.arch.sp, 4))}')",
after=(
f"{self.cmd} --b --n 4 $sp",
"pi print(f'*** *sp={u32(gef.memory.read(gef.arch.sp, 4))}')",
"pi print(f'*** *sp={u32(gef.memory.read(gef.arch.sp, 4)):#x}')",
)
)
self.assertNoException(res)
lines = findlines("*** *sp=", res)
self.assertEqual(len(lines), 2)
self.assertEqual(lines[1], "*** *sp=2425393296") # 4*nop -> 0x90909090 -> 2425393296
self.assertEqual(lines[1], "*** *sp=0x90909090")
@pytest.mark.skipif(ARCH not in ("i686", "x86_64"), reason=f"Skipped for {ARCH}")
def test_cmd_nop_as_bytes_invalid_end_address(self):
# Make sure we error out if writing nops into an unmapped or RO area
res = gdb_run_silent_cmd(
f"{self.cmd} --b --n 5 0x1337000+0x1000-4",
target=_target("mmap-known-address")
)
self.assertNoException(res)
self.assertIn("Cannot patch instruction at 0x1337ffc: reaching unmapped area", res)
# We had an off-by-one bug where we couldn't write the last byte before
# an unmapped area. Make sure that we can now.
res = gdb_run_silent_cmd(
f"{self.cmd} --b --n 4 0x1337000+0x1000-4",
target=_target("mmap-known-address"),
after="pi print(f'*** *mem={u32(gef.memory.read(0x1337ffc, 4)):#x}')",
)
self.assertNoException(res)
self.assertNotIn("Cannot patch instruction at 0x1337ffc: reaching unmapped area", res)
lines = findlines("*** *mem=", res)
self.assertEqual(len(lines), 1)
self.assertEqual(lines[0], "*** *mem=0x90909090")