Fix utimensat to avoid passing uninitialized values into WASI calls. #291
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Previously, utimensat would leave the mtim and/or atim timestamps uninitialized when the `MTIM_NOW` or `ATIM_NOW` were in use, because that means the respective timestamps are not used. However, clang now automatically adds `noundef` to the arguments in functions like `__wasi_path_filestat_set_times`, and there are cases where simplifycfg can see paths where the uninitialized values are passed to those `noundef` arguments. To fix this, change the utimens code to zero out the timestamps when they aren't in use, to avoid passing uninitialized arguments.
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Why does clang automatically add |
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I'm not current on the latest thinking about uninitialized variables, but I imagine it's considered UB in C to pass uninitialized values as function arguments. Clang 14 appears to automatically add noundef to all C function arguments. |
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Previously, utimensat would leave the mtim and/or atim timestamps
uninitialized when the
MTIM_NOWorATIM_NOWwere in use, becausethat means the respective timestamps are not used.
However, clang now automatically adds
noundefto the arguments infunctions like
__wasi_path_filestat_set_times, and there are caseswhere simplifycfg can see paths where the uninitialized values are
passed to those
noundefarguments.To fix this, change the utimens code to zero out the timestamps when
they aren't in use, to avoid passing uninitialized arguments.