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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: b2197755b2
("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>
This commit is contained in:
parent
66e58e0ef8
commit
b165585795
1 changed files with 12 additions and 2 deletions
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@ -295,6 +295,15 @@ static const struct file_operations bpffs_map_fops = {
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.release = bpffs_map_release,
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};
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static int bpffs_obj_open(struct inode *inode, struct file *file)
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{
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return -EIO;
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}
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static const struct file_operations bpffs_obj_fops = {
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.open = bpffs_obj_open,
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};
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static int bpf_mkobj_ops(struct dentry *dentry, umode_t mode, void *raw,
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const struct inode_operations *iops,
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const struct file_operations *fops)
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@ -314,7 +323,8 @@ static int bpf_mkobj_ops(struct dentry *dentry, umode_t mode, void *raw,
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static int bpf_mkprog(struct dentry *dentry, umode_t mode, void *arg)
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{
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return bpf_mkobj_ops(dentry, mode, arg, &bpf_prog_iops, NULL);
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return bpf_mkobj_ops(dentry, mode, arg, &bpf_prog_iops,
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&bpffs_obj_fops);
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}
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static int bpf_mkmap(struct dentry *dentry, umode_t mode, void *arg)
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@ -322,7 +332,7 @@ static int bpf_mkmap(struct dentry *dentry, umode_t mode, void *arg)
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struct bpf_map *map = arg;
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return bpf_mkobj_ops(dentry, mode, arg, &bpf_map_iops,
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map->btf ? &bpffs_map_fops : NULL);
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map->btf ? &bpffs_map_fops : &bpffs_obj_fops);
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}
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static struct dentry *
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