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Add more comments about the changes in #1273 (#1274)

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Alan Li 2022-10-12 20:17:35 +08:00 committed by GitHub
parent fc33d6fb7c
commit fbedf0b497
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1 changed files with 7 additions and 1 deletions
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8
pwndbg/heap/ptmalloc.py
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@ -1089,7 +1089,13 @@ class HeuristicHeap(Heap):
try:
tmp_next = int(tmp_arena["next"])
except (gdb.MemoryError, gdb.error, OverflowError):
# tmp_arena->next is not valid, break
# Since we are just guessing the correct address by reading every possible address, it has high possibility to get the following errors when reading an invalid address:
# 1) If we try to read unmapped memory, we will get `gdb.MemoryError`
# 2) `tmp_arena["next"]` will try to use `gdb.Value(tmp_next+offset)` during `pwndbg.gdblib.memory.poi`, but if `tmp_next+offset` >= 2 ** 64 which is too big for GDB, it will raise `OverflowError: int too big to convert`
# 3) Since GDB's Python API is buggy sometimes, to catch some weird things we missed, we also catch the `gdb.error` here :)
# (So `gdb.error` is not necessary, this can be removed if we are sure the above first two cases can cover all possible errors)
# if `&tmp_arena->next` is not valid, the linked list is broken, break this while loop and try `addr+pwndbg.gdblib.arch.ptrsize` again
break
if found:
break