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Message-ID: <20131211225616.GA3483@fieldses.org>
Date: Wed, 11 Dec 2013 17:56:16 -0500
From: "J. Bruce Fields" <bfields@...ldses.org>
To: Jeff Layton <jlayton@...hat.com>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
nfs-ganesha-devel@...ts.sourceforge.net,
samba-technical@...ts.samba.org
Subject: Re: [PATCH v3 1/6] locks: consolidate common code in the
flock_to_posix_lock routines
On Wed, Dec 11, 2013 at 02:07:41PM -0500, Jeff Layton wrote:
> On Wed, 11 Dec 2013 10:19:31 -0500
> "J. Bruce Fields" <bfields@...ldses.org> wrote:
...
> > + if (l->l_len > 0)
> > + fl->fl_end = fl->fl_start + l->l_len - 1;
> > + else if (l->l_len < 0) {
> > + fl->fl_end = start - 1;
>
> Erm... I think this is not quite right...
>
> "start" is uninitialized here. I think this should be:
>
> fl->fl_end = fl->fl_start - 1
>
> With that too, we can get rid of the local "start" variable. I think
> this may explain why I'm tripping over the BUG() in locks_remove_file.
Yep.
One other bug: I think l_start < 0 is actually fine in the
SEEK_CUR/SEEK_END cases.
With that fixed and another comment (though I don't know how much it
helps), it looks like the below.
--b.
commit 052f395880af17919d4c13037deed581f367b2a8
Author: J. Bruce Fields <bfields@...hat.com>
Date: Tue Dec 10 18:14:28 2013 -0500
locks: fix posix lock range overflow handling
In the 32-bit case fcntl assigns f_pos and i_size to a 32-bit off_t,
with probably incorrect results.
So instead let's return -EOVERFLOW as described in SUSv3, whenever "the
smallest or, if l_len is non-zero, the largest offset of any byte in the
requested segment cannot be represented correctly in an object of type
off_t."
While we're here, do some cleanup including consolidating code for the
flock and flock64 cases.
Signed-off-by: J. Bruce Fields <bfields@...hat.com>
diff --git a/fs/locks.c b/fs/locks.c
index 92a0f0a..39f2ca9 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -344,48 +344,42 @@ static int assign_type(struct file_lock *fl, long type)
return 0;
}
-/* 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)
+static int flock_to_posix_lock_common(struct file *filp, struct file_lock *fl,
+ struct flock64 *l, loff_t offset_max)
{
- off_t start, end;
-
switch (l->l_whence) {
case SEEK_SET:
- start = 0;
+ fl->fl_start = 0;
break;
case SEEK_CUR:
- start = filp->f_pos;
+ fl->fl_start = filp->f_pos;
break;
case SEEK_END:
- start = i_size_read(file_inode(filp));
+ 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;
+ if (l->l_len > offset_max - fl->fl_start)
+ return -EOVERFLOW;
+ if (fl->fl_start + l->l_len < 0)
+ 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;
-
+ if (l->l_len > 0)
+ fl->fl_end = fl->fl_start + l->l_len - 1;
+ else if (l->l_len < 0) {
+ 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;
@@ -396,50 +390,32 @@ static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
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)
+{
+ struct flock64 ll = {
+ .l_type = l->l_type,
+ .l_whence = l->l_whence,
+ .l_start = l->l_start,
+ .l_len = l->l_len,
+ };
+
+ /*
+ * The use of OFFT_OFFSET_MAX here ensures we return -EOVERFLOW
+ * if the start or end of the lock could not be represented as
+ * an off_t, following SUSv3.
+ */
+ return flock_to_posix_lock_common(filp, fl, &ll, OFFT_OFFSET_MAX);
+}
+
#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);
+ return flock_to_posix_lock_common(filp, fl, l, OFFSET_MAX);
}
#endif
diff --git a/include/uapi/asm-generic/fcntl.h b/include/uapi/asm-generic/fcntl.h
index 95e46c8..36025f7 100644
--- a/include/uapi/asm-generic/fcntl.h
+++ b/include/uapi/asm-generic/fcntl.h
@@ -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 */
--
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