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| author | KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> | 2010-10-01 14:20:22 -0700 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2010-10-25 21:18:21 -0400 |
| commit | 4a3956c790290efeb647bbb0c3a90476bb57800e (patch) | |
| tree | 18abb41325273d23ae271e49627f01054c5baeb6 /fs | |
| parent | ba10f486658c0ca1bc84c936f6a996e40d071453 (diff) | |
| download | lwn-4a3956c790290efeb647bbb0c3a90476bb57800e.tar.gz lwn-4a3956c790290efeb647bbb0c3a90476bb57800e.zip | |
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/<pid>/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 <fengguang.wu@intel.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/proc/base.c | 2 | ||||
| -rw-r--r-- | fs/read_write.c | 28 |
2 files changed, 26 insertions, 4 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c index dc5d5f51f3fe..fb2a5abd4e4f 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -771,6 +771,8 @@ static const struct file_operations proc_single_file_operations = { static int mem_open(struct inode* inode, struct file* file) { file->private_data = (void*)((long)current->self_exec_id); + /* OK to pass negative loff_t, we can catch out-of-range */ + file->f_mode |= FMODE_UNSIGNED_OFFSET; return 0; } 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( |