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attr: fix out-of-bounds read with huge attribute names
There is an out-of-bounds read possible when parsing gitattributes that have an attribute that is 2^31+1 bytes long. This is caused due to an integer overflow when we assign the result of strlen(3P) to an `int`, where we use the wrapped-around value in a subsequent call to memcpy(3P). The following code reproduces the issue: blob=$(perl -e 'print "a" x 2147483649 . " attr"' | git hash-object -w --stdin) git update-index --add --cacheinfo 100644,$blob,.gitattributes git check-attr --all file AddressSanitizer:DEADLYSIGNAL ================================================================= ==8451==ERROR: AddressSanitizer: SEGV on unknown address 0x7f93efa00800 (pc 0x7f94f1f8f082 bp 0x7ffddb59b3a0 sp 0x7ffddb59ab28 T0) ==8451==The signal is caused by a READ memory access. #0 0x7f94f1f8f082 (/usr/lib/libc.so.6+0x176082) #1 0x7f94f2047d9c in __interceptor_strspn /usr/src/debug/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:752 #2 0x560e190f7f26 in parse_attr_line attr.c:375 #3 0x560e190f9663 in handle_attr_line attr.c:660 #4 0x560e190f9ddd in read_attr_from_index attr.c:769 #5 0x560e190f9f14 in read_attr attr.c:797 #6 0x560e190fa24e in bootstrap_attr_stack attr.c:867 #7 0x560e190fa4a5 in prepare_attr_stack attr.c:902 #8 0x560e190fb5dc in collect_some_attrs attr.c:1097 #9 0x560e190fb93f in git_all_attrs attr.c:1128 #10 0x560e18e6136e in check_attr builtin/check-attr.c:67 #11 0x560e18e61c12 in cmd_check_attr builtin/check-attr.c:183 #12 0x560e18e15993 in run_builtin git.c:466 #13 0x560e18e16397 in handle_builtin git.c:721 #14 0x560e18e16b2b in run_argv git.c:788 #15 0x560e18e17991 in cmd_main git.c:926 #16 0x560e190ae2bd in main common-main.c:57 #17 0x7f94f1e3c28f (/usr/lib/libc.so.6+0x2328f) #18 0x7f94f1e3c349 in __libc_start_main (/usr/lib/libc.so.6+0x23349) #19 0x560e18e110e4 in _start ../sysdeps/x86_64/start.S:115 AddressSanitizer can not provide additional info. SUMMARY: AddressSanitizer: SEGV (/usr/lib/libc.so.6+0x176082) ==8451==ABORTING Fix this bug by converting the variable to a `size_t` instead. Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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