top: simplify command line reading

function                                             old     new   delta
cmdline_to_line_buf_and_print                          -      48     +48
read_cmdline                                         326     327      +1
display_topmem_process_list                          523     505     -18
display_process_list                                1186    1161     -25
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/2 up/down: 49/-43)              Total: 6 bytes

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

2 files changed, 26 insertions, 18 deletions

diff --git a/libbb/procps.c b/libbb/procps.c
index 3256fafc5..fc31c075d 100644
--- a/libbb/procps.c
+++ b/libbb/procps.c
@@ -558,22 +558,29 @@ int FAST_FUNC read_cmdline(char *buf, int col, unsigned pid, const char *comm)
 	if (sz < 0)
 		return sz;
 	if (sz > 0) {
-		const char *base;
+		const char *program_basename;
 		int comm_len;
 
 		buf[sz] = '\0';
 		while (--sz >= 0 && buf[sz] == '\0')
 			continue;
-		/* Prevent basename("process foo/bar") = "bar" */
-		strchrnul(buf, ' ')[0] = '\0';
-		base = bb_basename(buf); /* before we replace argv0's NUL with space */
+
+		/* Find "program" in "[-][/PATH/TO/]program" */
+		strchrnul(buf, ' ')[0] = '\0'; /* prevent basename("program foo/bar") = "bar" */
+		program_basename = bb_basename(buf[0] == '-' ? buf + 1 : buf);
+		/* ^^^ note: must do it *before* replacing argv0's NUL with space */
+
+		/* Prevent stuff like this:
+		 *  echo 'sleep 999; exit' >`printf '\ec'`; sh ?c
+		 * messing up top and ps output (or worse).
+		 * This also replaces NULs with spaces, converting
+		 * list of NUL-strings into one string.
+		 */
 		while (sz >= 0) {
 			if ((unsigned char)(buf[sz]) < ' ')
 				buf[sz] = ' ';
 			sz--;
 		}
-		if (base[0] == '-') /* "-sh" (login shell)? */
-			base++;
 
 		/* If comm differs from argv0, prepend "{comm} ".
 		 * It allows to see thread names set by prctl(PR_SET_NAME).
@@ -587,7 +594,7 @@ int FAST_FUNC read_cmdline(char *buf, int col, unsigned pid, const char *comm)
 		 * I prefer to still treat argv0 "process foo bar"
 		 * as 'equal' to comm "process".
 		 */
-		if (strncmp(base, comm, comm_len) != 0) {
+		if (strncmp(program_basename, comm, comm_len) != 0) {
 			comm_len += 3;
 			if (col > comm_len)
 				memmove(buf + comm_len, buf, col - comm_len);
diff --git a/procps/top.c b/procps/top.c
index bff9f7c4f..96b3e2d4e 100644
--- a/procps/top.c
+++ b/procps/top.c
@@ -602,6 +602,15 @@ static void parse_meminfo(unsigned long meminfo[MI_MAX])
 	fclose(f);
 }
 
+static void cmdline_to_line_buf_and_print(unsigned offset, unsigned pid, const char *comm)
+{
+	int width = G.scr_width - offset;
+	if (width > 1) /* wider than to fit just the NUL? */
+		read_cmdline(G.line_buf + offset, width, pid, comm);
+//TODO: read_cmdline() sanitizes control chars, but not chars above 0x7e
+	print_line_buf();
+}
+
 static unsigned long display_header(void)
 {
 	char *buf;
@@ -789,9 +798,7 @@ static NOINLINE void display_process_list(void)
 				IF_FEATURE_TOP_SMP_PROCESS(, s->last_seen_on_cpu)
 				IF_FEATURE_TOP_CPU_USAGE_PERCENTAGE(, SHOW_STAT(pcpu))
 		);
-		if ((int)(G.scr_width - col) > 1)
-			read_cmdline(G.line_buf + col, G.scr_width - col, s->pid, s->comm);
-		print_line_buf();
+		cmdline_to_line_buf_and_print(col, s->pid, s->comm);
 		/* printf(" %d/%d %lld/%lld", s->pcpu, total_pcpu,
 			cur_jif.busy - prev_jif.busy, cur_jif.total - prev_jif.total); */
 		s++;
@@ -910,14 +917,12 @@ static void ulltoa4_and_space(unsigned long long ul, char buf[5])
 
 static NOINLINE void display_topmem_process_list(void)
 {
-#define HDR_STR "  PID   VSZ VSZRW   RSS (SHR) DIRTY (SHR) STACK"
-#define MIN_WIDTH sizeof(HDR_STR)
 	const topmem_status_t *s = topmem + G_scroll_ofs;
 	char *cp, ch;
 
 	display_topmem_header();
 
-	strcpy(G.line_buf, HDR_STR " COMMAND");
+	strcpy(G.line_buf, "  PID   VSZ VSZRW   RSS (SHR) DIRTY (SHR) STACK COMMAND");
 	/* Mark the ^FIELD^ we sort by */
 	cp = &G.line_buf[5 + sort_field * 6];
 	ch = "^_"[inverted];
@@ -949,13 +954,9 @@ static NOINLINE void display_topmem_process_list(void)
 		ulltoa5_and_space(s->dirty_sh, &G.line_buf[6*6]);
 		ulltoa5_and_space(s->stack   , &G.line_buf[7*6]);
 		G.line_buf[8*6] = '\0';
-		if ((int)(G.scr_width - MIN_WIDTH) > 1)
-			read_cmdline(&G.line_buf[8*6], G.scr_width - MIN_WIDTH, s->pid, s->comm);
-		print_line_buf();
+		cmdline_to_line_buf_and_print(8*6, s->pid, s->comm);
 		s++;
 	}
-#undef HDR_STR
-#undef MIN_WIDTH
 }
 
 #endif /* end TOPMEM support */