PATH_MAX Includes Nul Fix

PATCH New Rusty Russell 1 participant 1 message Nov 22, 2001

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Rusty Russell

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2001-11-22 07:46 UTC #0 lore raw

PATCH 1/1 PATH_MAX Includes Nul Fix

Linus, please apply.

Grepping for PATH_MAX in the kernel reveals some ambiguity in whether PATH_MAX includes a the trailing NUL or not. From Andrew Josey <[email protected]> (via Chris Yeoh):

POSIX has long had an ambiguity in the area about whether the null byte is included in the PATH_MAX (it basically said both ways in the 1990 text). The POSIX.1a draft (the amendment to POSIX.1-1990) and XPG4 went with including the null byte in PATH_MAX, and the POSIX 1003.1-200x revision (Austin Group) and Single UNIX Specification Version 3 also continue this way.

Note that to reach compliance, glibc will need to be adjusted as well.

include/linux/limits.h +1 -1

diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.4.14/include/linux/limits.h working-2.4.14-pathmax/include/linux/limits.h
@@ -11,7 +11,7 @@
 #define MAX_CANON        255	/* size of the canonical input queue */
 #define MAX_INPUT        255	/* size of the type-ahead buffer */
 #define NAME_MAX         255	/* # chars in a file name */
-#define PATH_MAX        4095	/* # chars in a path name */
+#define PATH_MAX        4096	/* # chars in a path name including nul */
 #define PIPE_BUF        4096	/* # bytes in atomic write to a pipe */
 
 #define RTSIG_MAX	  32

fs/dcache.c +1 -1

diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.4.14/fs/dcache.c working-2.4.14-pathmax/fs/dcache.c
@@ -1262,7 +1262,7 @@
 		panic("Cannot create buffer head SLAB cache");
 
 	names_cachep = kmem_cache_create("names_cache", 
-			PATH_MAX + 1, 0, 
+			PATH_MAX, 0, 
 			SLAB_HWCACHE_ALIGN, NULL, NULL);
 	if (!names_cachep)
 		panic("Cannot create names SLAB cache");

fs/namei.c +3 -2

diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.4.14/fs/namei.c working-2.4.14-pathmax/fs/namei.c
@@ -99,16 +99,17 @@
  * kernel data space before using them..
  *
  * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
+ * PATH_MAX includes the nul terminator --RR.
  */
 static inline int do_getname(const char *filename, char *page)
 {
 	int retval;
-	unsigned long len = PATH_MAX + 1;
+	unsigned long len = PATH_MAX;
 
 	if ((unsigned long) filename >= TASK_SIZE) {
 		if (!segment_eq(get_fs(), KERNEL_DS))
 			return -EFAULT;
-	} else if (TASK_SIZE - (unsigned long) filename < PATH_MAX + 1)
+	} else if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
 		len = TASK_SIZE - (unsigned long) filename;
 
 	retval = strncpy_from_user((char *)page, filename, len);

scripts/mkdep.c +1 -1

diff -urN -I \$.*\$ --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal linux-2.4.14/scripts/mkdep.c working-2.4.14-pathmax/scripts/mkdep.c
@@ -218,7 +218,7 @@
 void add_path(const char * name)
 {
 	struct path_struct *path;
-	char resolved_path[PATH_MAX+1];
+	char resolved_path[PATH_MAX];
 	const char *name2;
 
 	if (strcmp(name, ".")) {

--
Premature optmztion is rt of all evl. --DK