commit 28b51a7f199d003b309e9dab52457759d5fd7691

Author: Jakub Klinkovský <1289205+lahwaacz@users.noreply.github.com>

Date:   Thu May 23 21:05:56 2024 +0200

    Fix buffer overflow in Markdown parser

    This fixes a buffer overflow that happened when parsing a bad Markdown

    file with an unclosed emphasis nested in other elements, such as

    ```markdown

    > __af_err af_flip(af_array *out, const af_array in, const unsigned dim)__

    ```

    This snippet comes from the ArrayFire repository [1]. The problem was

    found after the refactoring [2] that introduced std::string_view in the

    code. The `std::string_view::operator[]` has bounds checking enabled

    when the macro `_GLIBCXX_ASSERTIONS` is defined, which is the case of

    Arch Linux build system.

    [1] https://github.com/arrayfire/arrayfire/blob/0a25d36238aa1eee3b775d3584937ca65b0a1807/docs/pages/matrix_manipulation.md

    [2] https://github.com/doxygen/doxygen/commit/f4e37514325abe4aa6aeecbc96e9e3e027885aef

diff --git a/src/markdown.cpp b/src/markdown.cpp

index 10429edd5..df00900b0 100644

--- a/src/markdown.cpp

+++ b/src/markdown.cpp

@@ -661,6 +661,11 @@ size_t Markdown::Private::findEmphasisChar(std::string_view data, char c, size_t

                      data[i]!='\\' && data[i]!='@' &&

                      !(data[i]=='/' && data[i-1]=='<') && // html end tag also ends emphasis

                      data[i]!='\n') i++;

+    // avoid overflow (unclosed emph token)

+    if (i==size)

+    {

+      return 0;

+    }

     //printf("findEmphasisChar: data=[%s] i=%d c=%c\n",data,i,data[i]);

     // not counting escaped chars or characters that are unlikely