Prevent heap-buffer-overflow #4797
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When running repack while doing repo writes, `packfile_load__cb()` can see some temporary files in the directory that are bigger than the usual, and makes `memcmp` overflow on the `p->pack_name` string. ASAN detected this. This just uses `strncmp`, that should not have any performance impact and is safe for comparing strings of different sizes.
```
ERROR: AddressSanitizer: heap-buffer-overflow on address 0x61200001a3f3 at pc 0x7f4a9e1976ec bp 0x7ffc1f80e100 sp 0x7ffc1f80d8b0
READ of size 89 at 0x61200001a3f3 thread T0
SCARINESS: 26 (multi-byte-read-heap-buffer-overflow)
#0 0x7f4a9e1976eb in __interceptor_memcmp.part.78 (/build/cfgr-admin#link-tree/libtools_build_sanitizers_asan-ubsan-py.so+0xcf6eb)
#1 0x7f4a518c5431 in packfile_load__cb /build/libgit2/0.27.0/src/libgit2-0.27.0/src/odb_pack.c:213
#2 0x7f4a518d9582 in git_path_direach /build/libgit2/0.27.0/src/libgit2-0.27.0/src/path.c:1134
#3 0x7f4a518c58ad in pack_backend__refresh /build/libgit2/0.27.0/src/libgit2-0.27.0/src/odb_pack.c:347
libgit2#4 0x7f4a518c1b12 in git_odb_refresh /build/libgit2/0.27.0/src/libgit2-0.27.0/src/odb.c:1511
libgit2#5 0x7f4a518bff5f in git_odb__freshen /build/libgit2/0.27.0/src/libgit2-0.27.0/src/odb.c:752
libgit2#6 0x7f4a518c17d4 in git_odb_stream_finalize_write /build/libgit2/0.27.0/src/libgit2-0.27.0/src/odb.c:1415
libgit2#7 0x7f4a51b9d015 in Repository_write /build/pygit2/0.27.0/src/pygit2-0.27.0/src/repository.c:509
```
|
Makes sense to me, thanks for fixing this! |
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When running repack while doing repo writes,
packfile_load__cb()can see some temporary files in the directory that are bigger than the usual, and makesmemcmpoverflow on thep->pack_namestring. ASAN detected this. This just usesstrncmp, that should not have any performance impact and is safe for comparing strings of different sizes.