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This commit adds explicit `i1 > 0` and `i2 > 0` checks around those array accesses to prevent invalid negative indexing. Signed-off-by: Alex Guo --- Fix buffer underflow in xdl_build_script Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1976%2Fmugitya03%2Fbuf-1-v1 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1976/mugitya03/buf-1-v1 Pull-Request: https://github.com/git/git/pull/1976 xdiff/xdiffi.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/xdiff/xdiffi.c b/xdiff/xdiffi.c index 5a96e36dfbe..2e983965328 100644 --- a/xdiff/xdiffi.c +++ b/xdiff/xdiffi.c @@ -951,9 +951,10 @@ int xdl_build_script(xdfenv_t *xe, xdchange_t **xscr) { * Trivial. Collects "groups" of changes and creates an edit script. */ for (i1 = xe->xdf1.nrec, i2 = xe->xdf2.nrec; i1 >= 0 || i2 >= 0; i1--, i2--) - if (rchg1[i1 - 1] || rchg2[i2 - 1]) { - for (l1 = i1; rchg1[i1 - 1]; i1--); - for (l2 = i2; rchg2[i2 - 1]; i2--); + if ((i1 > 0 && rchg1[i1 - 1]) || + (i2 > 0 && rchg2[i2 - 1])) { + for (l1 = i1; i1 > 0 && rchg1[i1 - 1]; i1--); + for (l2 = i2; i2 > 0 && rchg2[i2 - 1]; i2--); if (!(xch = xdl_add_change(cscr, i1, i2, l1 - i1, l2 - i2))) { xdl_free_script(cscr); base-commit: 8613c2bb6cd16ef530dc5dd74d3b818a1ccbf1c0 -- gitgitgadget