Messages in this thread Patch in this message | | | Subject | Re: [PATCH 00/23] Removal of binary sysctl support | From | (Eric W. Biederman) | Date | Thu, 19 Nov 2009 09:49:28 -0800 |
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Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> writes:
> Acked-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> > > But please wait a bit. We need to solve the twist below.
Agreed.
> Indeed. TOMOYO and AppArmor need a hint for prepending "/proc" prefix. > A simple implementation which adds one bit to task_struct is shown below. > In this way, not only the file permission checks inside dentry_open() > but also the directory permission checks inside vfs_path_lookup() can be > prepended "/proc" prefix. AppArmor might want to prepend "/proc" inside > vfs_path_lookup().
There don't appear to be any security hooks in vfs_path_lookup(). > > Regards. > ---------------------------------------- > [PATCH 1/2] sysctl: Add in_sysctl flag to task_struct. > > Pathname based access control prepends "/proc" prefix to the pathname obtained > by traversing ctl_table tree when binary sysctl is requested. > > Now, binary sysctl code was rewritten to use internal vfs mount of /proc but > currently there is no hint which can give pathname based access control a > chance to prepend "/proc" prefix.
Actually there is.
> [PATCH 1/2] TOMOYO: prepend /proc prefix for binary sysctl. > > The pathname obtained by binary_sysctl() starts with "/sys". > This patch prepends "/proc" prefix if the pathname was obtained inside > binary_sysctl() so that TOMOYO checks a pathname which starts with "/proc/sys". > > Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> > --- > security/tomoyo/realpath.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > --- sysctl-2.6.orig/security/tomoyo/realpath.c > +++ sysctl-2.6/security/tomoyo/realpath.c > @@ -108,6 +108,14 @@ int tomoyo_realpath_from_path2(struct pa > spin_unlock(&dcache_lock); > path_put(&root); > path_put(&ns_root); > + /* Prepend "/proc" prefix if binary_sysctl(). */ > + if (!IS_ERR(sp) && current->in_sysctl) { > + sp -= 5; > + if (sp >= newname) > + memcpy(sp, "/proc", 5); > + else > + sp = ERR_PTR(-ENOMEM); > + } > } > if (IS_ERR(sp)) > error = PTR_ERR(sp);
Instead of current->in_sysctl we can just look at the path and see if it is the root of the mount chain and if the fs is proc.
Something like:
diff --git a/security/tomoyo/realpath.c b/security/tomoyo/realpath.c index 5f2e332..0b55faa 100644 --- a/security/tomoyo/realpath.c +++ b/security/tomoyo/realpath.c @@ -108,6 +108,15 @@ int tomoyo_realpath_from_path2(struct path *path, char *newname, spin_unlock(&dcache_lock); path_put(&root); path_put(&ns_root); + /* Prepend "/proc" prefix if using internal proc vfs mount. */ + if (!IS_ERR(sp) && (path->mnt->mnt_parent == path->mnt) && + (strcmp(path->mnt->mnt_sb->s_type->name, "proc") == 0)) { + sp -= 5; + if (sp >= newname) + memcpy(sp, "/proc", 5); + else + sp = ERR_PTR(-ENOMEM); + } } if (IS_ERR(sp)) error = PTR_ERR(sp); Eric
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