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 <phil@xxxxxx> --- .../ipt-restore/0011-noflush-empty-line_0 | 16 ++++++++++++++++ iptables/xtables-restore.c | 8 +++++--- 2 files changed, 21 insertions(+), 3 deletions(-) create mode 100755 iptables/tests/shell/testcases/ipt-restore/0011-noflush-empty-line_0 diff --git a/iptables/tests/shell/testcases/ipt-restore/0011-noflush-empty-line_0 b/iptables/tests/shell/testcases/ipt-restore/0011-noflush-empty-line_0 new file mode 100755 index 0000000000000..bea1a690bb624 --- /dev/null +++ b/iptables/tests/shell/testcases/ipt-restore/0011-noflush-empty-line_0 @@ -0,0 +1,16 @@ +#!/bin/bash -e + +# make sure empty lines won't break --noflush + +cat <<EOF | $XT_MULTI iptables-restore --noflush +# just a comment followed by innocent empty line + +*filter +-A FORWARD -j ACCEPT +COMMIT +EOF + +EXPECT='Chain FORWARD (policy ACCEPT) +target prot opt source destination +ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 ' +diff -u <(echo "$EXPECT") <($XT_MULTI iptables -n -L FORWARD) diff --git a/iptables/xtables-restore.c b/iptables/xtables-restore.c index 63cc15cee9621..fb2ac8b5c12a3 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++; -- 2.24.1
