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Maniphest T3248

mpiutil.c:501:37: runtime error: unsigned integer overflow: 0 - 1 cannot be represented in type 'unsigned long'
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Description

Compiled libgcrypt 1.7.8 with bleading edge clang-5 ( 5.0.0 (trunk 305735)) and UBSan on Ubuntu 16.04 x64. Used the following flags:

-O2 -fno-omit-frame-pointer -g -fsanitize=address -fsanitize=undefined -fsanitize=integer -fsanitize-coverage=trace-pc-guard -fno-sanitize-recover=undefined -fsanitize=float-divide-by-zero -fsanitize=float-cast-overflow -fsanitize-undefined-trap-on-error -fno-sanitize-recover=all

Ran the following test:

libgcrypt-1.7.8/tests/fips186-dsa
mpiutil.c:501:37: runtime error: unsigned integer overflow: 0 - 1 cannot be represented in type 'unsigned long'
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior mpiutil.c:501:37 in

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Event Timeline

geeknik created this task.Jul 4 2017, 3:11 AM
• gniibe closed this task as Invalid.Jul 4 2017, 4:58 AM
• gniibe claimed this task.
• gniibe triaged this task as Low priority.
• gniibe added a subscriber: • gniibe.

It is intentionally used.
And in the C programming language, it is defined that unsigned integer never overflows (it is computed as modulo 2).

• gniibe mentioned this in T3245: cipher-gcm-intel-pclmul.c:418:17: runtime error: unsigned integer overflow: 0 - 1 cannot be represented in type 'size_t' (aka 'unsigned long').Jul 4 2017, 5:06 AM