From: Hadi Chokr <hadichokr@icloud.com>
Date: Thu, 9 Jul 2026 13:28:41 +0000 (+0000)
Subject: subids: find_free_range(): skip empty ranges
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=36072d80dbae2137f6190caf6906e7cb911102c7;p=thirdparty%2Fshadow.git

subids: find_free_range(): skip empty ranges

Empty (count == 0) ranges constrain nothing, so skip them instead of
processing them.  Besides documenting that invariant, this keeps the
range-end computation, first - 1LL + range->count, away from the
count == 0 corner, where for first == 0 it would produce -1 through
unsigned long wrap-around and an implementation-defined conversion on
64-bit systems.

Such entries exist in the wild, since old useradd versions used to
create them, so they are still accepted by the parser; they are only
ignored during allocation.

Co-authored-by: Dan Anderson <https://github.com/MillaFleurs>

Reviewed-by: Alejandro Colomar <alx@kernel.org>
Signed-off-by: Hadi Chokr <hadichokr@icloud.com>
---

diff --git a/lib/subordinateio.c b/lib/subordinateio.c
index af3b2807c..97994168a 100644
--- a/lib/subordinateio.c
+++ b/lib/subordinateio.c
@@ -360,6 +360,9 @@ find_free_range(struct commonio_db *db, id_t min, id_t max, unsigned long count)
 	while (NULL != (range = commonio_next(db))) {
 		intmax_t  first, last;
 
+		if (range->count == 0)
+			continue;
+
 		first = range->start;
 		last = first - 1LL + range->count;