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authorDaniel Borkmann <daniel@iogearbox.net>2018-06-08 18:10:34 +0200
committerAlexei Starovoitov <ast@kernel.org>2018-06-08 10:58:48 -0700
commitb16558579576c8f2781062b638600f68954b1827 (patch)
tree02f1506ca24d7f8deadb17e4b33b314ea3f6e604 /kernel/bpf
parent66e58e0ef80a56a1d7857b6ce121141563cdd93e (diff)
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bpf: implement dummy fops for bpf objects
syzkaller was able to trigger the following warning in do_dentry_open(): WARNING: CPU: 1 PID: 4508 at fs/open.c:778 do_dentry_open+0x4ad/0xe40 fs/open.c:778 Kernel panic - not syncing: panic_on_warn set ... CPU: 1 PID: 4508 Comm: syz-executor867 Not tainted 4.17.0+ #90 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: [...] vfs_open+0x139/0x230 fs/open.c:908 do_last fs/namei.c:3370 [inline] path_openat+0x1717/0x4dc0 fs/namei.c:3511 do_filp_open+0x249/0x350 fs/namei.c:3545 do_sys_open+0x56f/0x740 fs/open.c:1101 __do_sys_openat fs/open.c:1128 [inline] __se_sys_openat fs/open.c:1122 [inline] __x64_sys_openat+0x9d/0x100 fs/open.c:1122 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x49/0xbe Problem was that prog and map inodes in bpf fs did not implement a dummy file open operation that would return an error. The patch in do_dentry_open() checks whether f_ops are present and if not bails out with an error. While this may be fine, we really shouldn't be throwing a warning though. Thus follow the model similar to bad_file_ops and reject the request unconditionally with -EIO. Fixes: b2197755b263 ("bpf: add support for persistent maps/progs") Reported-by: syzbot+2e7fcab0f56fdbb330b8@syzkaller.appspotmail.com Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf')
-rw-r--r--kernel/bpf/inode.c14
1 files changed, 12 insertions, 2 deletions
diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index ed13645bd80c..76efe9a183f5 100644
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -295,6 +295,15 @@ static const struct file_operations bpffs_map_fops = {
.release = bpffs_map_release,
};
+static int bpffs_obj_open(struct inode *inode, struct file *file)
+{
+ return -EIO;
+}
+
+static const struct file_operations bpffs_obj_fops = {
+ .open = bpffs_obj_open,
+};
+
static int bpf_mkobj_ops(struct dentry *dentry, umode_t mode, void *raw,
const struct inode_operations *iops,
const struct file_operations *fops)
@@ -314,7 +323,8 @@ static int bpf_mkobj_ops(struct dentry *dentry, umode_t mode, void *raw,
static int bpf_mkprog(struct dentry *dentry, umode_t mode, void *arg)
{
- return bpf_mkobj_ops(dentry, mode, arg, &bpf_prog_iops, NULL);
+ return bpf_mkobj_ops(dentry, mode, arg, &bpf_prog_iops,
+ &bpffs_obj_fops);
}
static int bpf_mkmap(struct dentry *dentry, umode_t mode, void *arg)
@@ -322,7 +332,7 @@ static int bpf_mkmap(struct dentry *dentry, umode_t mode, void *arg)
struct bpf_map *map = arg;
return bpf_mkobj_ops(dentry, mode, arg, &bpf_map_iops,
- map->btf ? &bpffs_map_fops : NULL);
+ map->btf ? &bpffs_map_fops : &bpffs_obj_fops);
}
static struct dentry *