From b777f3fd619ac2af507ffd3e7c5fe0d6e36e81f2 Mon Sep 17 00:00:00 2001 From: Jeff King Date: Tue, 23 Jul 2019 15:27:05 -0400 Subject: xdiff: clamp function context indices in post-image MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit After finding a function line for --function-context in the pre-image, xdl_emit_diff() calculates the equivalent line in the post-image. It assumes that the lines between changes are the same on both sides. If the option --ignore-blank-lines was also given then this is not necessarily true. Clamp the calculation results for start and end of the function context to prevent out-of-bounds array accesses. Note that this _just_ fixes the case where our mismatch sends us off the beginning of the file. There are likely other cases where our assumption causes us to go to the wrong line within the file. Nobody has developed a test case yet, and the ultimate fix is likely more complicated than this patch. But this at least prevents a segfault in the meantime. Credit for finding the bug goes to "Liu Wei of Tencent Security Xuanwu Lab". Reported-by: 刘炜 Helped-by: René Scharfe Signed-off-by: Jeff King Signed-off-by: Junio C Hamano --- xdiff/xemit.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'xdiff') diff --git a/xdiff/xemit.c b/xdiff/xemit.c index 7778dc2b19..30713ae9a9 100644 --- a/xdiff/xemit.c +++ b/xdiff/xemit.c @@ -210,7 +210,7 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb, if (fs1 < 0) fs1 = 0; if (fs1 < s1) { - s2 -= s1 - fs1; + s2 = XDL_MAX(s2 - (s1 - fs1), 0); s1 = fs1; } } @@ -232,7 +232,7 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb, if (fe1 < 0) fe1 = xe->xdf1.nrec; if (fe1 > e1) { - e2 += fe1 - e1; + e2 = XDL_MIN(e2 + (fe1 - e1), xe->xdf2.nrec); e1 = fe1; } -- cgit v1.2.3