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vim-patch:9.0.1899: potential buffer overflow in PBYTE macro

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Problem:  potential buffer overflow in PBYTE macro
Solution: Check returned memline length

closes: vim/vim#13083

the PBYTE macro is used to put byte c at a position lp of the returned
memline. However, in case of unexpected errors ml_get_buf() may return
either "???" or an empty line in which case it is quite likely that we
are causing a buffer overrun.

Therefore, switch the macro PBYTE (which is only used in ops.c anyhow)
to a function, that verifies that we will only try to access within the
given length of the buffer.

Also, since the macro is only used in ops.c, move the definition from
macros.h to ops.c

ffb13674d1

Co-authored-by: Christian Brabandt <cb@256bit.org>
This commit is contained in:
Jan Edmund Lazo
2025-12-21 23:59:28 -05:00
parent efacb10709
commit 1afdcb8f2b
1 changed files with 12 additions and 3 deletions
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15
src/nvim/ops.c
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@@ -1046,11 +1046,20 @@ static void mb_adjust_opend(oparg_T *oap)
}
}
/// Put character 'c' at position 'lp'
static inline void pbyte(pos_T lp, int c)
/// put byte 'c' at position 'lp', but
/// verify, that the position to place
/// is actually safe
static void pbyte(pos_T lp, int c)
{
assert(c <= UCHAR_MAX);
*(ml_get_buf_mut(curbuf, lp.lnum) + lp.col) = (char)c;
char *p = ml_get_buf_mut(curbuf, lp.lnum);
colnr_T len = curbuf->b_ml.ml_line_len;
// safety check
if (lp.col >= len) {
lp.col = (len > 1 ? len - 2 : 0);
}
*(p + lp.col) = (char)c;
if (!curbuf_splice_pending) {
extmark_splice_cols(curbuf, (int)lp.lnum - 1, lp.col, 1, 1, kExtmarkUndo);
}