Fix OOB access due to multiple backspaces #273
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@tats My fix posted in the issue was not right. This is a slightly different solution. |
Commit 419ca82 (Fix m17n backspace handling causes out-of-bounds write in checkType) introduced an incomplete fix. In function checkType we store the length of the previous multi-char character in a buffer plens_buffer with pointer plens pointing to the current position inside the buffer. When encountering a backspace plens is set to the previous position without a bounds check. This will lead to plens being out of bounds if we get more backspaces than we have processed multi-char characters before. If we are at the beginning of the buffer do not decrement and set plen (the current length) to 0. This also fixes GH Issue #270 [BUG] Out of bound read in Strnew_size , Str.c:61 If the above explanation does sound weird it's because I didn't fully grok that function. :-)
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Merged, thank you. |
This was referenced Jul 18, 2023
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Commit 419ca82 (Fix m17n backspace handling causes out-of-bounds
write in checkType) introduced an incomplete fix.
In function checkType we store the length of the previous multi-char
character in a buffer plens_buffer with pointer plens pointing to the
current position inside the buffer. When encountering a backspace plens
is set to the previous position without a bounds check. This will lead
to plens being out of bounds if we get more backspaces than we have
processed multi-char characters before.
If we are at the beginning of the buffer do not decrement and set plen
(the current length) to 0.
This also fixes GH Issue #270 [BUG] Out of bound read in Strnew_size ,
Str.c:61
If the above explanation does sound weird it's because I didn't fully
grok that function. :-)