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| author | Daniel Borkmann <daniel@iogearbox.net> | 2018-06-08 18:10:34 +0200 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2018-06-08 10:58:48 -0700 |
| commit | b16558579576c8f2781062b638600f68954b1827 (patch) | |
| tree | 02f1506ca24d7f8deadb17e4b33b314ea3f6e604 /kernel/bpf | |
| parent | 66e58e0ef80a56a1d7857b6ce121141563cdd93e (diff) | |
| download | linux-stable-b16558579576c8f2781062b638600f68954b1827.tar.gz linux-stable-b16558579576c8f2781062b638600f68954b1827.tar.bz2 linux-stable-b16558579576c8f2781062b638600f68954b1827.zip | |
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.c | 14 |
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 * |