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Date: Fri, 18 Dec 2020 16:06:16 -0800 From: Stephen Brennan <stephen.s.brennan@...cle.com> To: Alexey Dobriyan <adobriyan@...il.com> Cc: Stephen Brennan <stephen.s.brennan@...cle.com>, James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>, linux-security-module@...r.kernel.org, Paul Moore <paul@...l-moore.com>, Stephen Smalley <stephen.smalley.work@...il.com>, Eric Paris <eparis@...isplace.org>, selinux@...r.kernel.org, Casey Schaufler <casey@...aufler-ca.com>, Eric Biederman <ebiederm@...ssion.com>, Alexander Viro <viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, Matthew Wilcox <willy@...radead.org> Subject: [PATCH v3 2/2] proc: ensure security hook is called after exec Smack needs its security_task_to_inode() hook to be called when a task execs a new executable. Store the self_exec_id of the task and call the hook via pid_update_inode() whenever the exec_id changes. Signed-off-by: Stephen Brennan <stephen.s.brennan@...cle.com> --- As discussed on the v2 of the patch, this should allow Smack to receive a security_task_to_inode() call only when the uid/gid changes, or when the task execs a new binary. I have verified that this doesn't change the performance of the patch set, and that we do fall out of RCU walk on tasks which have recently exec'd. fs/proc/base.c | 4 +++- fs/proc/internal.h | 5 ++++- 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index 4b246e9bd5df..ad59e92e8433 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1917,6 +1917,7 @@ struct inode *proc_pid_make_inode(struct super_block * sb, } task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid); + ei->exec_id = task->self_exec_id; security_task_to_inode(task, inode); out: @@ -1965,6 +1966,7 @@ void pid_update_inode(struct task_struct *task, struct inode *inode) task_dump_owner(task, inode->i_mode, &inode->i_uid, &inode->i_gid); inode->i_mode &= ~(S_ISUID | S_ISGID); + PROC_I(inode)->exec_id = task->self_exec_id; security_task_to_inode(task, inode); } @@ -1979,7 +1981,7 @@ static bool pid_inode_needs_update(struct task_struct *task, struct inode *inode task_dump_owner(task, inode->i_mode, &uid, &gid); if (!uid_eq(uid, inode->i_uid) || !gid_eq(gid, inode->i_gid)) return true; - return false; + return task->self_exec_id != PROC_I(inode)->exec_id; } /* diff --git a/fs/proc/internal.h b/fs/proc/internal.h index f60b379dcdc7..1df9b039dfc3 100644 --- a/fs/proc/internal.h +++ b/fs/proc/internal.h @@ -92,7 +92,10 @@ union proc_op { struct proc_inode { struct pid *pid; - unsigned int fd; + union { + unsigned int fd; + u32 exec_id; + }; union proc_op op; struct proc_dir_entry *pde; struct ctl_table_header *sysctl; -- 2.25.1
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