use use SEEK_MAX to validate user lseek arguments

Add SEEK_MAX and use it to validate lseek arguments from userspace.

Signed-off-by: Chris Snook <csnook@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 3 insertions, 2 deletions

diff --git a/fs/read_write.c b/fs/read_write.c
index 0642a1691d15..4d03008f015b 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -139,7 +139,7 @@ asmlinkage off_t sys_lseek(unsigned int fd, off_t offset, unsigned int origin)
                 goto bad;
 
         retval = -EINVAL;
-        if (origin <= 2) {
+        if (origin <= SEEK_MAX) {
                 loff_t res = vfs_llseek(file, offset, origin);
                 retval = res;
                 if (res != (loff_t)retval)
@@ -166,7 +166,7 @@ asmlinkage long sys_llseek(unsigned int fd, unsigned long offset_high,
                 goto bad;
 
         retval = -EINVAL;
-        if (origin > 2)
+        if (origin > SEEK_MAX)
                 goto out_putf;
 
         offset = vfs_llseek(file, ((loff_t) offset_high << 32) | offset_low,
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 020a8426e10a..986b5d5d369f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -30,6 +30,7 @@
 #define SEEK_SET        0       /* seek relative to beginning of file */
 #define SEEK_CUR        1       /* seek relative to current file position */
 #define SEEK_END        2       /* seek relative to end of file */
+#define SEEK_MAX        SEEK_END
 
 /* And dynamically-tunable limits and defaults: */
 struct files_stat_struct {