Otherwise child processes can consume xargs input:
$ yes /etc/issue | head -n1000 | xargs -i cat | wc -l
0
$ yes /etc/issue | head -n1000 | ./busybox xargs -i cat | wc -l
628
After this patch (comparing busybox to xargs):
$ yes /etc/issue | head -n1000 | ./busybox xargs cat | wc -l
2000
$ yes /etc/issue | head -n1000 | xargs cat | wc -l
2000
$ yes /etc/issue | head -n1000 | ./busybox xargs -i cat | wc -l
0
$ yes /etc/issue | head -n1000 | xargs -i cat | wc -l
0
Refs: https://savannah.gnu.org/bugs/?3992
Signed-off-by: Azat Khuzhin <[email protected]>
---
findutils/xargs.c | 50 +++++++++++++++++++++++++++++++------------
testsuite/xargs.tests | 19 ++++++++++++++++
2 files changed, 55 insertions(+), 14 deletions(-)
diff --git a/findutils/xargs.c b/findutils/xargs.c
index 890c37534..8105a2043 100644
--- a/findutils/xargs.c
+++ b/findutils/xargs.c
@@ -108,11 +108,19 @@ struct globals {
char **argv;
const char *repl_str;
char eol_ch;
+#endif
+#if ENABLE_FEATURE_XARGS_SUPPORT_ARGS_FILE
+ char *opt_a;
#endif
const char *eof_str;
int idx;
int fd_tty;
+ /* Used to replace stdin for spawned commands, to forbid access to
xargs stdin */
+ int fd_null;
+ /* Used to restore "stdin" (a.k.a. input file with commands) after
command spawning */
int fd_stdin;
+ /* Original stdin of xargs program, that will be used for spawned
programs in case of -a */
+ int fd_stdin_orig;
#if ENABLE_FEATURE_XARGS_SUPPORT_PARALLEL
int running_procs;
int max_procs;
@@ -132,6 +140,7 @@ struct globals {
setup_common_bufsiz(); \
IF_FEATURE_XARGS_SUPPORT_REPL_STR(G.repl_str = "{}";) \
IF_FEATURE_XARGS_SUPPORT_REPL_STR(G.eol_ch = '\n';) \
+ IF_FEATURE_XARGS_SUPPORT_ARGS_FILE(G.opt_a = NULL;) \
/* Even zero values are set because we are NOEXEC applet */ \
G.eof_str = NULL; \
G.idx = 0; \
@@ -189,8 +198,16 @@ static int xargs_exec(void)
{
int status;
- if (option_mask32 & OPT_STDIN_TTY)
- xdup2(G.fd_tty, STDIN_FILENO);
+ int stdin_fd = G.fd_stdin_orig;
+ if (option_mask32 & OPT_STDIN_TTY) {
+ stdin_fd = G.fd_tty;
+ } else {
+#if ENABLE_FEATURE_XARGS_SUPPORT_ARGS_FILE
+ if (!G.opt_a)
+ stdin_fd = G.fd_null;
+#endif
+ }
+ xdup2(stdin_fd, STDIN_FILENO);
#if !ENABLE_FEATURE_XARGS_SUPPORT_PARALLEL
status = spawn_and_wait(G.args);
@@ -278,8 +295,7 @@ static int xargs_exec(void)
ret:
if (status != 0)
G.xargs_exitcode = status;
- if (option_mask32 & OPT_STDIN_TTY)
- xdup2(G.fd_stdin, STDIN_FILENO);
+ xdup2(G.fd_stdin, STDIN_FILENO);
return status;
}
@@ -624,8 +640,6 @@ int xargs_main(int argc UNUSED_PARAM, char **argv)
#else
#define read_args process_stdin
#endif
- IF_FEATURE_XARGS_SUPPORT_ARGS_FILE(char *opt_a = NULL;)
-
INIT_G();
opt = getopt32long(argv, OPTION_STR,
@@ -633,7 +647,7 @@ int xargs_main(int argc UNUSED_PARAM, char **argv)
&max_args, &max_chars, &G.eof_str, &G.eof_str
IF_FEATURE_XARGS_SUPPORT_REPL_STR(, &G.repl_str, &G.repl_str)
IF_FEATURE_XARGS_SUPPORT_PARALLEL(, &G.max_procs)
- IF_FEATURE_XARGS_SUPPORT_ARGS_FILE(, &opt_a)
+ IF_FEATURE_XARGS_SUPPORT_ARGS_FILE(, &G.opt_a)
);
#if ENABLE_FEATURE_XARGS_SUPPORT_PARALLEL
@@ -641,11 +655,6 @@ int xargs_main(int argc UNUSED_PARAM, char **argv)
G.max_procs = 100; /* let's not go crazy high */
#endif
-#if ENABLE_FEATURE_XARGS_SUPPORT_ARGS_FILE
- if (opt_a)
- xmove_fd(xopen(opt_a, O_RDONLY), 0);
-#endif
-
/* -E ""? You may wonder why not just omit -E?
* This is used for portability:
* old xargs was using "_" as default for -E / -e */
@@ -736,11 +745,24 @@ int xargs_main(int argc UNUSED_PARAM, char **argv)
store_param(argv[i]);
}
+ /* Preserve original stdin to reopen it for child in case of -a */
+ G.fd_stdin_orig = dup(STDIN_FILENO);
+ close_on_exec_on(G.fd_stdin_orig);
+
+#if ENABLE_FEATURE_XARGS_SUPPORT_ARGS_FILE
+ if (G.opt_a)
+ xmove_fd(xopen(G.opt_a, O_RDONLY), STDIN_FILENO);
+#endif
+
+ G.fd_stdin = dup(STDIN_FILENO);
+ close_on_exec_on(G.fd_stdin);
+
if (opt & OPT_STDIN_TTY) {
G.fd_tty = xopen(CURRENT_TTY, O_RDONLY);
close_on_exec_on(G.fd_tty);
- G.fd_stdin = dup(STDIN_FILENO);
- close_on_exec_on(G.fd_stdin);
+ } else {
+ G.fd_null = xopen("/dev/null", O_RDONLY);
+ close_on_exec_on(G.fd_null);
}
initial_idx = G.idx;
diff --git a/testsuite/xargs.tests b/testsuite/xargs.tests
index c5e7b99e9..77d7e8b2e 100755
--- a/testsuite/xargs.tests
+++ b/testsuite/xargs.tests
@@ -59,6 +59,25 @@ testing "xargs -n2" \
"1 2\n3 4\n5\n" \
"" "1 2 3 4 5\n"
+# ensure that programs that is run under xargs
+# will not have access to xargs stdin
+optional FEATURE_XARGS_SUPPORT_REPL_STR
+testing "xargs closes stdin" \
+ "xargs -i cat | wc -l" \
+ "0\n" \
+ "" \
+ "$(yes /etc/issue | head -n1000)"
+
+# ensure that cat will get original stdin in case of xargs has -a, so here it
+# will got "yes /etc/issue | head -n10", but due to stripping whitespaces it
+# will got only 9 lines
+optional FEATURE_XARGS_SUPPORT_REPL_STR FEATURE_XARGS_SUPPORT_ARGS_FILE
+testing "xargs closes stdin with -a" \
+ "xargs -a input -i cat | wc -l" \
+ "9\n" \
+ "/etc/issue" \
+ "$(yes /etc/issue | head -n10)"
+
SKIP=
optional FEATURE_XARGS_SUPPORT_QUOTES FEATURE_XARGS_SUPPORT_REPL_STR
--
2.47.1
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