From 4a3956c790290efeb647bbb0c3a90476bb57800e Mon Sep 17 00:00:00 2001 From: KAMEZAWA Hiroyuki Date: Fri, 1 Oct 2010 14:20:22 -0700 Subject: vfs: introduce FMODE_UNSIGNED_OFFSET for allowing negative f_pos Now, rw_verify_area() checsk f_pos is negative or not. And if negative, returns -EINVAL. But, some special files as /dev/(k)mem and /proc//mem etc.. has negative offsets. And we can't do any access via read/write to the file(device). So introduce FMODE_UNSIGNED_OFFSET to allow negative file offsets. Signed-off-by: Wu Fengguang Signed-off-by: KAMEZAWA Hiroyuki Cc: Al Viro Cc: Heiko Carstens Signed-off-by: Andrew Morton Signed-off-by: Al Viro --- fs/read_write.c | 28 ++++++++++++++++++++++++---- 1 file changed, 24 insertions(+), 4 deletions(-) (limited to 'fs/read_write.c') diff --git a/fs/read_write.c b/fs/read_write.c index e757ef26e4ce..9cd9d148105d 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -31,6 +31,20 @@ const struct file_operations generic_ro_fops = { EXPORT_SYMBOL(generic_ro_fops); +static int +__negative_fpos_check(struct file *file, loff_t pos, size_t count) +{ + /* + * pos or pos+count is negative here, check overflow. + * too big "count" will be caught in rw_verify_area(). + */ + if ((pos < 0) && (pos + count < pos)) + return -EOVERFLOW; + if (file->f_mode & FMODE_UNSIGNED_OFFSET) + return 0; + return -EINVAL; +} + /** * generic_file_llseek_unlocked - lockless generic llseek implementation * @file: file structure to seek on @@ -62,7 +76,9 @@ generic_file_llseek_unlocked(struct file *file, loff_t offset, int origin) break; } - if (offset < 0 || offset > inode->i_sb->s_maxbytes) + if (offset < 0 && __negative_fpos_check(file, offset, 0)) + return -EINVAL; + if (offset > inode->i_sb->s_maxbytes) return -EINVAL; /* Special lock needed here? */ @@ -137,7 +153,7 @@ loff_t default_llseek(struct file *file, loff_t offset, int origin) offset += file->f_pos; } retval = -EINVAL; - if (offset >= 0) { + if (offset >= 0 || !__negative_fpos_check(file, offset, 0)) { if (offset != file->f_pos) { file->f_pos = offset; file->f_version = 0; @@ -221,6 +237,7 @@ bad: } #endif + /* * rw_verify_area doesn't like huge counts. We limit * them to something that fits in "int" so that others @@ -238,8 +255,11 @@ int rw_verify_area(int read_write, struct file *file, loff_t *ppos, size_t count if (unlikely((ssize_t) count < 0)) return retval; pos = *ppos; - if (unlikely((pos < 0) || (loff_t) (pos + count) < 0)) - return retval; + if (unlikely((pos < 0) || (loff_t) (pos + count) < 0)) { + retval = __negative_fpos_check(file, pos, count); + if (retval) + return retval; + } if (unlikely(inode->i_flock && mandatory_lock(inode))) { retval = locks_mandatory_area( -- cgit v1.2.3-55-g7522