thodg/libgit2/tests/core

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  • Hash : 174b7a32
    Author : Patrick Steinhardt
    Date : 2019-09-19T12:24:06

    buffer: fix printing into out-of-memory buffer Before printing into a `git_buf` structure, we always call `ENSURE_SIZE` first. This macro will reallocate the buffer as-needed depending on whether the current amount of allocated bytes is sufficient or not. If `asize` is big enough, then it will just do nothing, otherwise it will call out to `git_buf_try_grow`. But in fact, it is insufficient to only check `asize`. When we fail to allocate any more bytes e.g. via `git_buf_try_grow`, then we set the buffer's pointer to `git_buf__oom`. Note that we touch neither `asize` nor `size`. So if we just check `asize > targetsize`, then we will happily let the caller of `ENSURE_SIZE` proceed with an out-of-memory buffer. As a result, we will print all bytes into the out-of-memory buffer instead, resulting in an out-of-bounds write. Fix the issue by having `ENSURE_SIZE` verify that the buffer is not marked as OOM. Add a test to verify that we're not writing into the OOM buffer.

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