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locks: fix posix lock range overflow handling

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In the 32-bit case fcntl assigns the 64-bit f_pos and i_size to a 32-bit
off_t.

The existing range checks also seem to depend on signed arithmetic
wrapping when it overflows.  In practice maybe that works, but we can be
more careful.  That also allows us to make a more reliable distinction
between -EINVAL and -EOVERFLOW.

Note that in the 32-bit case SEEK_CUR or SEEK_END might allow the caller
to set a lock with starting point no longer representable as a 32-bit
value.  We could return -EOVERFLOW in such cases, but the locks code is
capable of handling such ranges, so we choose to be lenient here.  The
only problem is that subsequent GETLK calls on such a lock will fail
with EOVERFLOW.

While we're here, do some cleanup including consolidating code for the
flock and flock64 cases.

Signed-off-by: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
This commit is contained in:
J. Bruce Fields 2014-02-03 12:13:08 -05:00 committed by Jeff Layton
parent 8c3cac5e6a
commit ef12e72a01
2 changed files with 54 additions and 93 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

144
fs/locks.c
View File

@ -344,105 +344,69 @@ static int assign_type(struct file_lock *fl, long type)
return 0;
}
static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
struct flock64 *l)
{
switch (l->l_whence) {
case SEEK_SET:
fl->fl_start = 0;
break;
case SEEK_CUR:
fl->fl_start = filp->f_pos;
break;
case SEEK_END:
fl->fl_start = i_size_read(file_inode(filp));
break;
default:
return -EINVAL;
}
if (l->l_start > OFFSET_MAX - fl->fl_start)
return -EOVERFLOW;
fl->fl_start += l->l_start;
if (fl->fl_start < 0)
return -EINVAL;
/* POSIX-1996 leaves the case l->l_len < 0 undefined;
POSIX-2001 defines it. */
if (l->l_len > 0) {
if (l->l_len - 1 > OFFSET_MAX - fl->fl_start)
return -EOVERFLOW;
fl->fl_end = fl->fl_start + l->l_len - 1;
} else if (l->l_len < 0) {
if (fl->fl_start + l->l_len < 0)
return -EINVAL;
fl->fl_end = fl->fl_start - 1;
fl->fl_start += l->l_len;
} else
fl->fl_end = OFFSET_MAX;
fl->fl_owner = current->files;
fl->fl_pid = current->tgid;
fl->fl_file = filp;
fl->fl_flags = FL_POSIX;
fl->fl_ops = NULL;
fl->fl_lmops = NULL;
return assign_type(fl, l->l_type);
}
/* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
* style lock.
*/
static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
struct flock *l)
{
off_t start, end;
struct flock64 ll = {
.l_type = l->l_type,
.l_whence = l->l_whence,
.l_start = l->l_start,
.l_len = l->l_len,
};
switch (l->l_whence) {
case SEEK_SET:
start = 0;
break;
case SEEK_CUR:
start = filp->f_pos;
break;
case SEEK_END:
start = i_size_read(file_inode(filp));
break;
default:
return -EINVAL;
}
/* POSIX-1996 leaves the case l->l_len < 0 undefined;
POSIX-2001 defines it. */
start += l->l_start;
if (start < 0)
return -EINVAL;
fl->fl_end = OFFSET_MAX;
if (l->l_len > 0) {
end = start + l->l_len - 1;
fl->fl_end = end;
} else if (l->l_len < 0) {
end = start - 1;
fl->fl_end = end;
start += l->l_len;
if (start < 0)
return -EINVAL;
}
fl->fl_start = start; /* we record the absolute position */
if (fl->fl_end < fl->fl_start)
return -EOVERFLOW;
fl->fl_owner = current->files;
fl->fl_pid = current->tgid;
fl->fl_file = filp;
fl->fl_flags = FL_POSIX;
fl->fl_ops = NULL;
fl->fl_lmops = NULL;
return assign_type(fl, l->l_type);
return flock64_to_posix_lock(filp, fl, &ll);
}
#if BITS_PER_LONG == 32
static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
struct flock64 *l)
{
loff_t start;
switch (l->l_whence) {
case SEEK_SET:
start = 0;
break;
case SEEK_CUR:
start = filp->f_pos;
break;
case SEEK_END:
start = i_size_read(file_inode(filp));
break;
default:
return -EINVAL;
}
start += l->l_start;
if (start < 0)
return -EINVAL;
fl->fl_end = OFFSET_MAX;
if (l->l_len > 0) {
fl->fl_end = start + l->l_len - 1;
} else if (l->l_len < 0) {
fl->fl_end = start - 1;
start += l->l_len;
if (start < 0)
return -EINVAL;
}
fl->fl_start = start; /* we record the absolute position */
if (fl->fl_end < fl->fl_start)
return -EOVERFLOW;
fl->fl_owner = current->files;
fl->fl_pid = current->tgid;
fl->fl_file = filp;
fl->fl_flags = FL_POSIX;
fl->fl_ops = NULL;
fl->fl_lmops = NULL;
return assign_type(fl, l->l_type);
}
#endif
/* default lease lock manager operations */
static void lease_break_callback(struct file_lock *fl)
{

3
include/uapi/asm-generic/fcntl.h
View File

@ -186,8 +186,6 @@ struct flock {
};
#endif
#ifndef CONFIG_64BIT
#ifndef HAVE_ARCH_STRUCT_FLOCK64
#ifndef __ARCH_FLOCK64_PAD
#define __ARCH_FLOCK64_PAD
@ -202,6 +200,5 @@ struct flock64 {
__ARCH_FLOCK64_PAD
};
#endif
#endif /* !CONFIG_64BIT */
#endif /* _ASM_GENERIC_FCNTL_H */