From 8e76391096f12212985c401ee83a67990aa27a29 Mon Sep 17 00:00:00 2001 From: Phil Sutter Date: Tue, 11 Feb 2020 16:52:59 +0100 Subject: xtables-restore: fix for --noflush and empty lines Lookahead buffer used for cache requirements estimate in restore --noflush separates individual lines with nul-chars. Two consecutive nul-chars are interpreted as end of buffer and remaining buffer content is skipped. Sadly, reading an empty line (i.e., one containing a newline character only) caused double nul-chars to appear in buffer as well, leading to premature stop when reading cached lines from buffer. To fix that, make use of xtables_restore_parse_line() skipping empty lines without calling strtok() and just leave the newline character in place. A more intuitive approach, namely skipping empty lines while buffering, is deliberately not chosen as that would cause wrong values in 'line' variable. Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1400 Fixes: 09cb517949e69 ("xtables-restore: Improve performance of --noflush operation") Signed-off-by: Phil Sutter Acked-by: Arturo Borrero Gonzalez --- iptables/xtables-restore.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'iptables/xtables-restore.c') diff --git a/iptables/xtables-restore.c b/iptables/xtables-restore.c index 63cc15ce..fb2ac8b5 100644 --- a/iptables/xtables-restore.c +++ b/iptables/xtables-restore.c @@ -293,11 +293,13 @@ void xtables_restore_parse(struct nft_handle *h, while (fgets(buffer, sizeof(buffer), p->in)) { size_t blen = strlen(buffer); - /* drop trailing newline; xtables_restore_parse_line() + /* Drop trailing newline; xtables_restore_parse_line() * uses strtok() which replaces them by nul-characters, * causing unpredictable string delimiting in - * preload_buffer */ - if (buffer[blen - 1] == '\n') + * preload_buffer. + * Unless this is an empty line which would fold into a + * spurious EoB indicator (double nul-char). */ + if (buffer[blen - 1] == '\n' && blen > 1) buffer[blen - 1] = '\0'; else blen++; -- cgit v1.2.3