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[iptables,2/5] libiptc: Avoid side-effect in memset() calls

Message ID 20180910213517.12160-3-phil@nwl.cc
State Accepted
Delegated to: Pablo Neira
Headers show
Series Fix for bugs indicated by covscan | expand

Commit Message

Phil Sutter Sept. 10, 2018, 9:35 p.m. UTC 
These calls to memset() are passed a length argument which exceeds
t->target.u.user.name's length by one byte and hence overwrite
t->target.u.user.revision as well (relying upon no padding to happen
between both).

Avoid this obscure behaviour by passing the correct field size and
explicitly overwriting 'revision' field.

Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 libiptc/libiptc.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
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Patch

diff --git a/libiptc/libiptc.c b/libiptc/libiptc.c
index a6e70571ad8d2..6eacdddd09a1c 100644
--- a/libiptc/libiptc.c
+++ b/libiptc/libiptc.c
@@ -1115,8 +1115,9 @@  static inline int iptcc_compile_rule (struct xtc_handle *h, STRUCT_REPLACE *repl
 		STRUCT_STANDARD_TARGET *t;
 		t = (STRUCT_STANDARD_TARGET *)GET_TARGET(r->entry);
 		/* memset for memcmp convenience on delete/replace */
-		memset(t->target.u.user.name, 0, FUNCTION_MAXNAMELEN);
+		memset(t->target.u.user.name, 0, XT_EXTENSION_MAXNAMELEN);
 		strcpy(t->target.u.user.name, STANDARD_TARGET);
+		t->target.u.user.revision = 0;
 		/* Jumps can only happen to builtin chains, so we
 		 * can safely assume that they always have a header */
 		t->verdict = r->jump->head_offset + IPTCB_CHAIN_START_SIZE;
@@ -1675,8 +1676,9 @@  iptcc_standard_map(struct rule_head *r, int verdict)
 		return 0;
 	}
 	/* memset for memcmp convenience on delete/replace */
-	memset(t->target.u.user.name, 0, FUNCTION_MAXNAMELEN);
+	memset(t->target.u.user.name, 0, XT_EXTENSION_MAXNAMELEN);
 	strcpy(t->target.u.user.name, STANDARD_TARGET);
+	t->target.u.user.revision = 0;
 	t->verdict = verdict;
 
 	r->type = IPTCC_R_STANDARD;