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From 36cf5177c724540aea5a42f9dc6ef5476f86179a Mon Sep 17 00:00:00 2001
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From: Phil Sutter <psutter@redhat.com>
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Date: Fri, 5 Nov 2021 16:06:45 +0100
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Subject: [PATCH] segtree: Fix segfault when restoring a huge interval set
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1908127
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Upstream Status: nftables commit baecd1cf26851
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commit baecd1cf26851a4c5b7d469206a488f14fe5b147
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Author: Phil Sutter <phil@nwl.cc>
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Date: Wed Jun 9 15:49:52 2021 +0200
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segtree: Fix segfault when restoring a huge interval set
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Restoring a set of IPv4 prefixes with about 1.1M elements crashes nft as
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set_to_segtree() exhausts the stack. Prevent this by allocating the
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pointer array on heap and make sure it is freed before returning to
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caller.
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With this patch in place, restoring said set succeeds with allocation of
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about 3GB of memory, according to valgrind.
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Signed-off-by: Phil Sutter <phil@nwl.cc>
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---
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src/segtree.c | 10 ++++++----
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1 file changed, 6 insertions(+), 4 deletions(-)
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diff --git a/src/segtree.c b/src/segtree.c
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index d6e3ce2..b852961 100644
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--- a/src/segtree.c
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+++ b/src/segtree.c
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@@ -414,10 +414,10 @@ static int set_to_segtree(struct list_head *msgs, struct set *set,
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struct expr *init, struct seg_tree *tree,
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bool add, bool merge)
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{
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- struct elementary_interval *intervals[init->size];
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+ struct elementary_interval **intervals;
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struct expr *i, *next;
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unsigned int n;
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- int err;
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+ int err = 0;
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/* We are updating an existing set with new elements, check if the new
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* interval overlaps with any of the existing ones.
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@@ -428,6 +428,7 @@ static int set_to_segtree(struct list_head *msgs, struct set *set,
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return err;
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}
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+ intervals = xmalloc_array(init->size, sizeof(intervals[0]));
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n = expr_to_intervals(init, tree->keylen, intervals);
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list_for_each_entry_safe(i, next, &init->expressions, list) {
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@@ -446,10 +447,11 @@ static int set_to_segtree(struct list_head *msgs, struct set *set,
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for (n = 0; n < init->size; n++) {
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err = ei_insert(msgs, tree, intervals[n], merge);
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if (err < 0)
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- return err;
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+ break;
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}
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- return 0;
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+ xfree(intervals);
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+ return err;
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}
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static bool segtree_needs_first_segment(const struct set *set,
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--
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2.31.1
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