Made new xreadlink function for libbb and changed applets to use it instead of

readlink(2).

13 files changed, 77 insertions, 90 deletions

diff --git a/Makefile b/Makefile
index 5713cdc68..91ed745c6 100644
--- a/Makefile
+++ b/Makefile
@@ -247,8 +247,8 @@ parse_mode.c parse_number.c perror_msg.c perror_msg_and_die.c print_file.c \
 process_escape_sequence.c read_package_field.c read_text_file_to_buffer.c \
 recursive_action.c safe_read.c safe_strncpy.c seek_ared_file.c syscalls.c \
 syslog_msg_with_name.c time_string.c trim.c untar.c unzip.c vdprintf.c \
-verror_msg.c vperror_msg.c wfopen.c xfuncs.c xgetcwd.c xregcomp.c interface.c \
-remove_file.c last_char_is.c
+verror_msg.c vperror_msg.c wfopen.c xfuncs.c xgetcwd.c xreadlink.c\
+xregcomp.c interface.c remove_file.c last_char_is.c
 LIBBB_OBJS=$(patsubst %.c,$(LIBBB)/%.o, $(LIBBB_CSRC))
 LIBBB_CFLAGS = -I$(LIBBB)
 ifneq ($(strip $(BB_SRC_DIR)),)
diff --git a/applets/busybox.c b/applets/busybox.c
index b4939e19d..badd53d79 100644
--- a/applets/busybox.c
+++ b/applets/busybox.c
@@ -37,21 +37,10 @@ typedef int (*__link_f)(const char *, const char *);
  */
 static char *busybox_fullpath()
 {
-        pid_t pid;
-        char path[256];
         char proc[256];
-        int len;
-
-        pid = getpid();
-        sprintf(proc, "/proc/%d/exe", pid);
-        len = readlink(proc, path, 256);
-        if (len != -1) {
-                path[len] = 0;
-        } else {
-                perror_msg("%s", proc);
-                return NULL;
-        }
-        return strdup(path);
+
+        sprintf(proc, "/proc/%d/exe", getpid());
+        return xreadlink(proc);
 }
 
 /* create (sym)links for each applet */
diff --git a/archival/tar.c b/archival/tar.c
index c168564ca..4bf8004ea 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -921,16 +921,10 @@ writeTarHeader(struct TarBallInfo *tbInfo, const char *header_name,
                 header.typeflag = LNKTYPE;
                 strncpy(header.linkname, tbInfo->hlInfo->name, sizeof(header.linkname));
         } else if (S_ISLNK(statbuf->st_mode)) {
-                int link_size=0;
-                char buffer[BUFSIZ];
+                char *lpath = xreadlink(real_name);
                 header.typeflag  = SYMTYPE;
-                link_size = readlink(real_name, buffer, sizeof(buffer) - 1);
-                if ( link_size < 0) {
-                        perror_msg("Error reading symlink '%s'", header.name);
-                        return ( FALSE);
-                }
-                buffer[link_size] = '\0';
-                strncpy(header.linkname, buffer, sizeof(header.linkname)); 
+                strncpy(header.linkname, lpath, sizeof(header.linkname)); 
+                free(lpath);
         } else if (S_ISDIR(statbuf->st_mode)) {
                 header.typeflag  = DIRTYPE;
                 strncat(header.name, "/", sizeof(header.name)); 
diff --git a/busybox.c b/busybox.c
index b4939e19d..badd53d79 100644
--- a/busybox.c
+++ b/busybox.c
@@ -37,21 +37,10 @@ typedef int (*__link_f)(const char *, const char *);
  */
 static char *busybox_fullpath()
 {
-        pid_t pid;
-        char path[256];
         char proc[256];
-        int len;
-
-        pid = getpid();
-        sprintf(proc, "/proc/%d/exe", pid);
-        len = readlink(proc, path, 256);
-        if (len != -1) {
-                path[len] = 0;
-        } else {
-                perror_msg("%s", proc);
-                return NULL;
-        }
-        return strdup(path);
+
+        sprintf(proc, "/proc/%d/exe", getpid());
+        return xreadlink(proc);
 }
 
 /* create (sym)links for each applet */
diff --git a/coreutils/ls.c b/coreutils/ls.c
index d24ba9866..c13b225fa 100644
--- a/coreutils/ls.c
+++ b/coreutils/ls.c
@@ -577,7 +577,7 @@ static struct dnode **list_dir(char *path)
 /*----------------------------------------------------------------------*/
 static int list_single(struct dnode *dn)
 {
-        int i, len;
+        int i;
         char scratch[BUFSIZ + 1];
 #ifdef BB_FEATURE_LS_TIMESTAMPS
         char *filetime;
@@ -688,16 +688,16 @@ static int list_single(struct dnode *dn)
                                 break;
                         case LIST_SYMLINK:
                                 if (S_ISLNK(dn->dstat.st_mode)) {
-                                        len= readlink(dn->fullname, scratch, (sizeof scratch)-1);
-                                        if (len > 0) {
-                                                scratch[len]= '\0';
-                                                printf(" -> %s", scratch);
+                                        char *lpath = xreadlink(dn->fullname);
+                                        if (lpath) {
+                                                printf(" -> %s", lpath);
 #ifdef BB_FEATURE_LS_FILETYPES
                                                 if (!stat(dn->fullname, &info)) {
                                                         append = append_char(info.st_mode);
                                                 }
 #endif
-                                                column += len+4;
+                                                column += strlen(lpath) + 4;
+                                                free(lpath);
                                         }
                                 }
                                 break;
diff --git a/include/libbb.h b/include/libbb.h
index a53e647d3..d2f9a9567 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -217,6 +217,7 @@ int ask_confirmation(void);
 int klogctl(int type, char * b, int len);
 
 char *xgetcwd(char *cwd);
+char *xreadlink(const char *path);
 char *concat_path_file(const char *path, const char *filename);
 int last_char_is(const char *s, const int c);
 
diff --git a/libbb/copy_file.c b/libbb/copy_file.c
index 2d18b6087..22684be74 100644
--- a/libbb/copy_file.c
+++ b/libbb/copy_file.c
@@ -196,19 +196,12 @@ int copy_file(const char *source, const char *dest, int flags)
                         return -1;
                 }
         } else if (S_ISLNK(source_stat.st_mode)) {
-                int size;
-                char buf[BUFSIZ + 1];
-
-                if ((size = readlink(source, buf, BUFSIZ)) < 0) {
-                        perror_msg("cannot read `%s'", source);
-                        return -1;
-                }
-                buf[size] = '\0';
-
-                if (symlink(buf, dest) < 0) {
+                char *lpath = xreadlink(source);
+                if (symlink(lpath, dest) < 0) {
                         perror_msg("cannot create symlink `%s'", dest);
                         return -1;
                 }
+                free(lpath);
 
 #if (__GLIBC__ >= 2) && (__GLIBC_MINOR__ >= 1)
                 if (flags & FILEUTILS_PRESERVE_STATUS)
diff --git a/libbb/libbb.h b/libbb/libbb.h
index a53e647d3..d2f9a9567 100644
--- a/libbb/libbb.h
+++ b/libbb/libbb.h
@@ -217,6 +217,7 @@ int ask_confirmation(void);
 int klogctl(int type, char * b, int len);
 
 char *xgetcwd(char *cwd);
+char *xreadlink(const char *path);
 char *concat_path_file(const char *path, const char *filename);
 int last_char_is(const char *s, const int c);
 
diff --git a/libbb/xreadlink.c b/libbb/xreadlink.c
new file mode 100644
index 000000000..66f63b883
--- /dev/null
+++ b/libbb/xreadlink.c
@@ -0,0 +1,34 @@
+/*
+ *  xreadlink.c - safe implementation of readlink
+ */
+
+#include <stdio.h>
+
+/*
+ * NOTE: This function returns a malloced char* that you will have to free
+ * yourself. You have been warned.
+ */
+
+#include <unistd.h>
+#include "libbb.h"
+
+extern char *xreadlink(const char *path)
+{                       
+        static const int GROWBY = 80; /* how large we will grow strings by */
+
+        char *buf = NULL;   
+        int bufsize = 0, readsize = 0;
+
+        do {
+                buf = xrealloc(buf, bufsize += GROWBY);
+                readsize = readlink(path, buf, bufsize); /* 1st try */
+                if (readsize == -1)
+                        perror_msg("%s:%s", applet_name, path);
+        }           
+        while (bufsize < readsize + 1);
+
+        buf[readsize] = '\0';
+
+        return buf;
+}       
+
diff --git a/ls.c b/ls.c
index d24ba9866..c13b225fa 100644
--- a/ls.c
+++ b/ls.c
@@ -577,7 +577,7 @@ static struct dnode **list_dir(char *path)
 /*----------------------------------------------------------------------*/
 static int list_single(struct dnode *dn)
 {
-        int i, len;
+        int i;
         char scratch[BUFSIZ + 1];
 #ifdef BB_FEATURE_LS_TIMESTAMPS
         char *filetime;
@@ -688,16 +688,16 @@ static int list_single(struct dnode *dn)
                                 break;
                         case LIST_SYMLINK:
                                 if (S_ISLNK(dn->dstat.st_mode)) {
-                                        len= readlink(dn->fullname, scratch, (sizeof scratch)-1);
-                                        if (len > 0) {
-                                                scratch[len]= '\0';
-                                                printf(" -> %s", scratch);
+                                        char *lpath = xreadlink(dn->fullname);
+                                        if (lpath) {
+                                                printf(" -> %s", lpath);
 #ifdef BB_FEATURE_LS_FILETYPES
                                                 if (!stat(dn->fullname, &info)) {
                                                         append = append_char(info.st_mode);
                                                 }
 #endif
-                                                column += len+4;
+                                                column += strlen(lpath) + 4;
+                                                free(lpath);
                                         }
                                 }
                                 break;
diff --git a/miscutils/readlink.c b/miscutils/readlink.c
index 74196e11d..226649544 100644
--- a/miscutils/readlink.c
+++ b/miscutils/readlink.c
@@ -30,21 +30,17 @@
 int readlink_main(int argc, char **argv)
 {
         char *buf = NULL;
-        int bufsize = 128, size = 128;
+
+        /* no options, no getopt */
 
         if (argc != 2)
                 show_usage();
 
-        while (bufsize < size + 1) {
-                bufsize *= 2;
-                buf = xrealloc(buf, bufsize);
-                size = readlink(argv[1], buf, bufsize);
-                if (size == -1)
-                        perror_msg_and_die("%s", argv[1]);
-        }
-
-        buf[size] = '\0';
+        buf = xreadlink(argv[1]);
         puts(buf);
+#ifdef BB_FEATURE_CLEAN_UP
+        free(buf);
+#endif
 
         return EXIT_SUCCESS;
 }
diff --git a/readlink.c b/readlink.c
index 74196e11d..226649544 100644
--- a/readlink.c
+++ b/readlink.c
@@ -30,21 +30,17 @@
 int readlink_main(int argc, char **argv)
 {
         char *buf = NULL;
-        int bufsize = 128, size = 128;
+
+        /* no options, no getopt */
 
         if (argc != 2)
                 show_usage();
 
-        while (bufsize < size + 1) {
-                bufsize *= 2;
-                buf = xrealloc(buf, bufsize);
-                size = readlink(argv[1], buf, bufsize);
-                if (size == -1)
-                        perror_msg_and_die("%s", argv[1]);
-        }
-
-        buf[size] = '\0';
+        buf = xreadlink(argv[1]);
         puts(buf);
+#ifdef BB_FEATURE_CLEAN_UP
+        free(buf);
+#endif
 
         return EXIT_SUCCESS;
 }
diff --git a/tar.c b/tar.c
index c168564ca..4bf8004ea 100644
--- a/tar.c
+++ b/tar.c
@@ -921,16 +921,10 @@ writeTarHeader(struct TarBallInfo *tbInfo, const char *header_name,
                 header.typeflag = LNKTYPE;
                 strncpy(header.linkname, tbInfo->hlInfo->name, sizeof(header.linkname));
         } else if (S_ISLNK(statbuf->st_mode)) {
-                int link_size=0;
-                char buffer[BUFSIZ];
+                char *lpath = xreadlink(real_name);
                 header.typeflag  = SYMTYPE;
-                link_size = readlink(real_name, buffer, sizeof(buffer) - 1);
-                if ( link_size < 0) {
-                        perror_msg("Error reading symlink '%s'", header.name);
-                        return ( FALSE);
-                }
-                buffer[link_size] = '\0';
-                strncpy(header.linkname, buffer, sizeof(header.linkname)); 
+                strncpy(header.linkname, lpath, sizeof(header.linkname)); 
+                free(lpath);
         } else if (S_ISDIR(statbuf->st_mode)) {
                 header.typeflag  = DIRTYPE;
                 strncat(header.name, "/", sizeof(header.name));