* [PATCH] ovl: skip getxattr of security labels
@ 2020-12-19 10:16 Amir Goldstein
2021-01-20 12:23 ` Amir Goldstein
0 siblings, 1 reply; 3+ messages in thread
From: Amir Goldstein @ 2020-12-19 10:16 UTC (permalink / raw)
To: Miklos Szeredi; +Cc: linux-unionfs, Michael Labriola
When inode has no listxattr op of its own (e.g. squashfs) vfs_listxattr
calls the LSM inode_listsecurity hooks to list the xattrs that LSMs will
intercept in inode_getxattr hooks.
When selinux LSM is installed but not initialized, it will list the
security.selinux xattr in inode_listsecurity, but will not intercept it
in inode_getxattr. This results in -ENODATA for a getxattr call for an
xattr returned by listxattr.
This situation was manifested as overlayfs failure to copy up lower
files from squashfs when selinux is built-in but not initialized,
because ovl_copy_xattr() iterates the lower inode xattrs by
vfs_listxattr() and vfs_getxattr().
ovl_copy_xattr() skips copy up of security labels that are indentified by
inode_copy_up_xattr LSM hooks, but it does that after vfs_getxattr().
Since we are not going to copy them, skip vfs_getxattr() of the security
labels.
Reported-by: Michael Labriola <michael.d.labriola@gmail.com>
Tested-by: Michael Labriola <michael.d.labriola@gmail.com>
Link: https://lore.kernel.org/linux-unionfs/2nv9d47zt7.fsf@aldarion.sourceruckus.org/
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
Miklos,
This is a workaround for a v5.9 selinux related regression reported by
Michael that caused copy up failure is a very specific configuration
involving lower squashfs and built-in but disabled selinux.
I've sent the bug fix to selinux list, so this patch is complementary.
I removed the stable/Fixes tags, because this patch does not cleanly
apply to v5.9 and is not the real bug fix.
Thanks,
Amir.
fs/overlayfs/copy_up.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index e5b616c93e11..0fed532efa68 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -84,6 +84,14 @@ int ovl_copy_xattr(struct super_block *sb, struct dentry *old,
if (ovl_is_private_xattr(sb, name))
continue;
+
+ error = security_inode_copy_up_xattr(name);
+ if (error < 0 && error != -EOPNOTSUPP)
+ break;
+ if (error == 1) {
+ error = 0;
+ continue; /* Discard */
+ }
retry:
size = vfs_getxattr(old, name, value, value_size);
if (size == -ERANGE)
@@ -107,13 +115,6 @@ int ovl_copy_xattr(struct super_block *sb, struct dentry *old,
goto retry;
}
- error = security_inode_copy_up_xattr(name);
- if (error < 0 && error != -EOPNOTSUPP)
- break;
- if (error == 1) {
- error = 0;
- continue; /* Discard */
- }
error = vfs_setxattr(new, name, value, size, 0);
if (error) {
if (error != -EOPNOTSUPP || ovl_must_copy_xattr(name))
--
2.25.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] ovl: skip getxattr of security labels
2020-12-19 10:16 [PATCH] ovl: skip getxattr of security labels Amir Goldstein
@ 2021-01-20 12:23 ` Amir Goldstein
2021-01-20 12:37 ` Miklos Szeredi
0 siblings, 1 reply; 3+ messages in thread
From: Amir Goldstein @ 2021-01-20 12:23 UTC (permalink / raw)
To: Miklos Szeredi; +Cc: overlayfs, Michael Labriola
On Sat, Dec 19, 2020 at 12:16 PM Amir Goldstein <amir73il@gmail.com> wrote:
>
> When inode has no listxattr op of its own (e.g. squashfs) vfs_listxattr
> calls the LSM inode_listsecurity hooks to list the xattrs that LSMs will
> intercept in inode_getxattr hooks.
>
> When selinux LSM is installed but not initialized, it will list the
> security.selinux xattr in inode_listsecurity, but will not intercept it
> in inode_getxattr. This results in -ENODATA for a getxattr call for an
> xattr returned by listxattr.
>
> This situation was manifested as overlayfs failure to copy up lower
> files from squashfs when selinux is built-in but not initialized,
> because ovl_copy_xattr() iterates the lower inode xattrs by
> vfs_listxattr() and vfs_getxattr().
>
> ovl_copy_xattr() skips copy up of security labels that are indentified by
> inode_copy_up_xattr LSM hooks, but it does that after vfs_getxattr().
> Since we are not going to copy them, skip vfs_getxattr() of the security
> labels.
>
> Reported-by: Michael Labriola <michael.d.labriola@gmail.com>
> Tested-by: Michael Labriola <michael.d.labriola@gmail.com>
> Link: https://lore.kernel.org/linux-unionfs/2nv9d47zt7.fsf@aldarion.sourceruckus.org/
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
>
> Miklos,
>
> This is a workaround for a v5.9 selinux related regression reported by
> Michael that caused copy up failure is a very specific configuration
> involving lower squashfs and built-in but disabled selinux.
>
> I've sent the bug fix to selinux list, so this patch is complementary.
> I removed the stable/Fixes tags, because this patch does not cleanly
> apply to v5.9 and is not the real bug fix.
>
Ping.
FWIW, the selinux bug fix should already be in next.
Thanks,
Amir.
>
> fs/overlayfs/copy_up.c | 15 ++++++++-------
> 1 file changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
> index e5b616c93e11..0fed532efa68 100644
> --- a/fs/overlayfs/copy_up.c
> +++ b/fs/overlayfs/copy_up.c
> @@ -84,6 +84,14 @@ int ovl_copy_xattr(struct super_block *sb, struct dentry *old,
>
> if (ovl_is_private_xattr(sb, name))
> continue;
> +
> + error = security_inode_copy_up_xattr(name);
> + if (error < 0 && error != -EOPNOTSUPP)
> + break;
> + if (error == 1) {
> + error = 0;
> + continue; /* Discard */
> + }
> retry:
> size = vfs_getxattr(old, name, value, value_size);
> if (size == -ERANGE)
> @@ -107,13 +115,6 @@ int ovl_copy_xattr(struct super_block *sb, struct dentry *old,
> goto retry;
> }
>
> - error = security_inode_copy_up_xattr(name);
> - if (error < 0 && error != -EOPNOTSUPP)
> - break;
> - if (error == 1) {
> - error = 0;
> - continue; /* Discard */
> - }
> error = vfs_setxattr(new, name, value, size, 0);
> if (error) {
> if (error != -EOPNOTSUPP || ovl_must_copy_xattr(name))
> --
> 2.25.1
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] ovl: skip getxattr of security labels
2021-01-20 12:23 ` Amir Goldstein
@ 2021-01-20 12:37 ` Miklos Szeredi
0 siblings, 0 replies; 3+ messages in thread
From: Miklos Szeredi @ 2021-01-20 12:37 UTC (permalink / raw)
To: Amir Goldstein; +Cc: overlayfs, Michael Labriola
On Wed, Jan 20, 2021 at 1:23 PM Amir Goldstein <amir73il@gmail.com> wrote:
>
> On Sat, Dec 19, 2020 at 12:16 PM Amir Goldstein <amir73il@gmail.com> wrote:
> > This is a workaround for a v5.9 selinux related regression reported by
> > Michael that caused copy up failure is a very specific configuration
> > involving lower squashfs and built-in but disabled selinux.
> >
> > I've sent the bug fix to selinux list, so this patch is complementary.
> > I removed the stable/Fixes tags, because this patch does not cleanly
> > apply to v5.9 and is not the real bug fix.
> >
>
> Ping.
Queued, thanks.
Miklos
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-01-20 13:46 UTC | newest]
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2020-12-19 10:16 [PATCH] ovl: skip getxattr of security labels Amir Goldstein
2021-01-20 12:23 ` Amir Goldstein
2021-01-20 12:37 ` Miklos Szeredi
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