We probably shouldn't ever get an xattr bigger than that, and the current check
of SSIZE_MAX is a bit too large.
Cc: Christian Brauner <[email protected]>
Cc: xingwei lee <[email protected]>
Cc: sam sun <[email protected]
Signed-off-by: Dominique Martinet <[email protected]>
---
fs/9p/xattr.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/9p/xattr.c b/fs/9p/xattr.c
index 8604e3377ee7..97f60b73bf16 100644
--- a/fs/9p/xattr.c
+++ b/fs/9p/xattr.c
@@ -37,8 +37,8 @@ ssize_t v9fs_fid_xattr_get(struct p9_fid *fid, const char *name,
if (attr_size > buffer_size) {
if (buffer_size)
retval = -ERANGE;
- else if (attr_size > SSIZE_MAX)
- retval = -EOVERFLOW;
+ else if (attr_size > XATTR_SIZE_MAX)
+ retval = -E2BIG;
else /* request to get the attr_size */
retval = attr_size;
} else {
---
base-commit: be3193e58ec210b2a72fb1134c2a0695088a911d
change-id: 20240304-xattr_maxsize-edf98c1a8c19
Best regards,
--
Dominique Martinet | Asmadeus
On Monday, March 4, 2024 1:42:43 PM CET Dominique Martinet wrote:
> We probably shouldn't ever get an xattr bigger than that, and the current check
> of SSIZE_MAX is a bit too large.
Maybe, OTOH e.g. ACLs (dynamic size) are implemented by storing them as xattrs
on 9p server as well, and this change somewhat expects server to run Linux as
well. So maybe s/XATTR_SIZE_MAX/KMALLOC_MAX_SIZE/ might be more appropriate,
considering that this patch is about fixing a potential kmalloc() warning?
Worth to mention in the commit log BTW what the issue was.
/Christian
On Mon, Mar 04, 2024 at 02:35:07PM +0100, Christian Schoenebeck wrote:
> On Monday, March 4, 2024 1:42:43 PM CET Dominique Martinet wrote:
> > We probably shouldn't ever get an xattr bigger than that, and the current check
> > of SSIZE_MAX is a bit too large.
>
> Maybe, OTOH e.g. ACLs (dynamic size) are implemented by storing them as xattrs
> on 9p server as well, and this change somewhat expects server to run Linux as
> well. So maybe s/XATTR_SIZE_MAX/KMALLOC_MAX_SIZE/ might be more appropriate,
> considering that this patch is about fixing a potential kmalloc() warning?
>
> Worth to mention in the commit log BTW what the issue was.
>
> /Christian
So the error is somewhat specific to filesystem capabilities which also
live in the xattr apis but Seth is working to get rid of them in there.
They currently use a special api vfs_getxattr_alloc() which is an
in-kernel api that does a racy query-size+allocate-buffer+retrieve-data
dance.
That api is used for fscaps, security labels, and other xattrs. And that
api doesn't do any size checks which probably should also be fixed now
that I write this.
@Seth?
On Mon, Mar 04, 2024 at 03:19:58PM +0100, Christian Brauner wrote:
> On Mon, Mar 04, 2024 at 02:35:07PM +0100, Christian Schoenebeck wrote:
> > On Monday, March 4, 2024 1:42:43 PM CET Dominique Martinet wrote:
> > > We probably shouldn't ever get an xattr bigger than that, and the current check
> > > of SSIZE_MAX is a bit too large.
> >
> > Maybe, OTOH e.g. ACLs (dynamic size) are implemented by storing them as xattrs
> > on 9p server as well, and this change somewhat expects server to run Linux as
> > well. So maybe s/XATTR_SIZE_MAX/KMALLOC_MAX_SIZE/ might be more appropriate,
> > considering that this patch is about fixing a potential kmalloc() warning?
> >
> > Worth to mention in the commit log BTW what the issue was.
> >
> > /Christian
>
> So the error is somewhat specific to filesystem capabilities which also
> live in the xattr apis but Seth is working to get rid of them in there.
>
> They currently use a special api vfs_getxattr_alloc() which is an
> in-kernel api that does a racy query-size+allocate-buffer+retrieve-data
> dance.
Yes, the patches I've sent does use vfs_getxattr_alloc() for fscaps
anymore.
> That api is used for fscaps, security labels, and other xattrs. And that
> api doesn't do any size checks which probably should also be fixed now
> that I write this.
>
> @Seth?
I agree. I don't see any reason that vfs_getxattr_alloc() shouldn't just
bail out with an error if the size of the xattr is >= XATTR_SIZE_MAX.
On Mon, Mar 04, 2024 at 08:35:46AM -0600, Seth Forshee wrote:
> On Mon, Mar 04, 2024 at 03:19:58PM +0100, Christian Brauner wrote:
> > On Mon, Mar 04, 2024 at 02:35:07PM +0100, Christian Schoenebeck wrote:
> > > On Monday, March 4, 2024 1:42:43 PM CET Dominique Martinet wrote:
> > > > We probably shouldn't ever get an xattr bigger than that, and the current check
> > > > of SSIZE_MAX is a bit too large.
> > >
> > > Maybe, OTOH e.g. ACLs (dynamic size) are implemented by storing them as xattrs
> > > on 9p server as well, and this change somewhat expects server to run Linux as
> > > well. So maybe s/XATTR_SIZE_MAX/KMALLOC_MAX_SIZE/ might be more appropriate,
> > > considering that this patch is about fixing a potential kmalloc() warning?
> > >
> > > Worth to mention in the commit log BTW what the issue was.
> > >
> > > /Christian
> >
> > So the error is somewhat specific to filesystem capabilities which also
> > live in the xattr apis but Seth is working to get rid of them in there.
> >
> > They currently use a special api vfs_getxattr_alloc() which is an
> > in-kernel api that does a racy query-size+allocate-buffer+retrieve-data
> > dance.
>
> Yes, the patches I've sent does use vfs_getxattr_alloc() for fscaps
> anymore.
Sorry, typo above. My patches do _not_ use vfs_getxattr_alloc() for
fscaps anymore.
>
> > That api is used for fscaps, security labels, and other xattrs. And that
> > api doesn't do any size checks which probably should also be fixed now
> > that I write this.
> >
> > @Seth?
>
> I agree. I don't see any reason that vfs_getxattr_alloc() shouldn't just
> bail out with an error if the size of the xattr is >= XATTR_SIZE_MAX.