>From 5c410df2df219dc9a68074afe5458b5563b89940 Mon Sep 17 00:00:00 2001 From: Tycho Andersen Date: Wed, 30 Sep 2015 14:53:48 -0600 Subject: [PATCH] use exactly one seccomp file per filter object Signed-off-by: Tycho Andersen --- kernel/seccomp.c | 37 ++++++++++++++++++++++++++++++++----- 1 file changed, 32 insertions(+), 5 deletions(-) diff --git a/kernel/seccomp.c b/kernel/seccomp.c index af58c49..ff3b1bd 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -60,6 +60,13 @@ struct seccomp_filter { atomic_t usage; struct seccomp_filter *prev; struct bpf_prog *prog; + + /* The file representing this seccomp_filter, if there is one. A 1:1 + * file:seccomp_filter mapping allows us to compare seccomp_filters via + * kcmp(KCMP_FILE, ...). + */ + struct file *seccomp_file; + struct mutex file_lock; }; /* Limit any path through the tree to 256KB worth of instructions. */ @@ -395,6 +402,7 @@ static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog) } atomic_set(&sfilter->usage, 1); + mutex_init(&sfilter->file_lock); return sfilter; } @@ -821,7 +829,14 @@ out_free: int seccomp_fd_release(struct inode *ino, struct file *f) { - seccomp_filter_decref(f->private_data); + struct seccomp_filter *filter = f->private_data; + + mutex_lock(&filter->file_lock); + filter->seccomp_file = NULL; + mutex_unlock(&filter->file_lock); + + seccomp_filter_decref(filter); + return 0; } @@ -1073,7 +1088,9 @@ long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter) long seccomp_get_filter_fd(struct task_struct *task, long n) { struct seccomp_filter *filter; + struct file *file; long fd; + int flags = O_RDONLY | O_CLOEXEC; if (task->seccomp.mode != SECCOMP_MODE_FILTER) return -EINVAL; @@ -1087,11 +1104,21 @@ long seccomp_get_filter_fd(struct task_struct *task, long n) if (!filter) return -EINVAL; - atomic_inc(&filter->usage); - fd = anon_inode_getfd("seccomp", &seccomp_fops, filter, - O_RDONLY | O_CLOEXEC); + fd = get_unused_fd_flags(flags); if (fd < 0) - seccomp_filter_decref(filter); + return fd; + + mutex_lock(&filter->file_lock); + file = filter->seccomp_file; + if (!file) { + atomic_inc(&filter->usage); + file = anon_inode_getfile("seccomp", &seccomp_fops, filter, + flags); + filter->seccomp_file = file; + } + mutex_unlock(&filter->file_lock); + + fd_install(fd, file); return fd; } -- 2.5.0