xargs: do not decrease orig_arg_max to negative values

Based on patch by Nguyễn Thái Ngọc Duy <pclouds@gmail.com>

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 25 insertions, 20 deletions

diff --git a/findutils/xargs.c b/findutils/xargs.c
index f5dbc7825..3785f1ec0 100644
--- a/findutils/xargs.c
+++ b/findutils/xargs.c
@@ -25,10 +25,10 @@
 /* COMPAT:  SYSV version defaults size (and has a max value of) to 470.
    We try to make it as large as possible. */
 #if !defined(ARG_MAX) && defined(_SC_ARG_MAX)
-#define ARG_MAX sysconf (_SC_ARG_MAX)
+# define ARG_MAX sysconf(_SC_ARG_MAX)
 #endif
-#ifndef ARG_MAX
-#define ARG_MAX 470
+#if !defined(ARG_MAX)
+# define ARG_MAX 470
 #endif
 
 
@@ -378,8 +378,6 @@ int xargs_main(int argc, char **argv)
         int child_error = 0;
         char *max_args, *max_chars;
         int n_max_arg;
-        size_t n_chars = 0;
-        long orig_arg_max;
         const char *eof_str = NULL;
         unsigned opt;
         size_t n_max_chars;
@@ -408,28 +406,35 @@ int xargs_main(int argc, char **argv)
                 argc++;
         }
 
-        orig_arg_max = ARG_MAX;
-        if (orig_arg_max == -1)
-                orig_arg_max = LONG_MAX;
-        orig_arg_max -= 2048;   /* POSIX.2 requires subtracting 2048 */
+        n_max_chars = ARG_MAX; /* might be calling sysconf(_SC_ARG_MAX) */
+        if (n_max_chars < 4*1024); /* paranoia */
+                n_max_chars = LONG_MAX;
+        /* The Open Group Base Specifications Issue 6:
+         * "The xargs utility shall limit the command line length such that
+         * when the command line is invoked, the combined argument
+         * and environment lists (see the exec family of functions
+         * in the System Interfaces volume of IEEE Std 1003.1-2001)
+         * shall not exceed {ARG_MAX}-2048 bytes".
+         */
+        n_max_chars -= 2048;
+        /* Sanity check for systems with huge ARG_MAX defines (e.g., Suns which
+         * have it at 1 meg).  Things will work fine with a large ARG_MAX but it
+         * will probably hurt the system more than it needs to; an array of this
+         * size is allocated.
+         */
+        if (n_max_chars > 20 * 1024)
+                n_max_chars = 20 * 1024;
 
         if (opt & OPT_UPTO_SIZE) {
-                n_max_chars = xatoul_range(max_chars, 1, orig_arg_max);
+                size_t n_chars = 0;
+                n_max_chars = xatoul_range(max_chars, 1, n_max_chars);
                 for (i = 0; i < argc; i++) {
                         n_chars += strlen(*argv) + 1;
                 }
-                if (n_max_chars < n_chars) {
+                if (n_max_chars <= n_chars) {
                         bb_error_msg_and_die("can't fit single argument within argument list size limit");
                 }
                 n_max_chars -= n_chars;
-        } else {
-                /* Sanity check for systems with huge ARG_MAX defines (e.g., Suns which
-                   have it at 1 meg).  Things will work fine with a large ARG_MAX but it
-                   will probably hurt the system more than it needs to; an array of this
-                   size is allocated.  */
-                if (orig_arg_max > 20 * 1024)
-                        orig_arg_max = 20 * 1024;
-                n_max_chars = orig_arg_max;
         }
         max_chars = xmalloc(n_max_chars);
 
@@ -442,9 +447,9 @@ int xargs_main(int argc, char **argv)
         while ((list = read_args(list, eof_str, n_max_chars, max_chars)) != NULL ||
                 !(opt & OPT_NO_EMPTY))
         {
+                size_t n_chars = 0;
                 opt |= OPT_NO_EMPTY;
                 n = 0;
-                n_chars = 0;
 #if ENABLE_FEATURE_XARGS_SUPPORT_TERMOPT
                 for (cur = list; cur;) {
                         n_chars += cur->length;