On Thu, Sep 10, 2020 at 05:46:21PM -0700, Alexei Starovoitov wrote: > On Thu, Sep 10, 2020 at 5:22 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote: > > > > Some kernels builds might inline vfs_getattr call within > > fstat syscall code path, so fentry/vfs_getattr trampoline > > is not called. > > > > I'm not sure how to handle this in some generic way other > > than use some other function, but that might get inlined at > > some point as well. > > It's great that we had the test and it failed. > Doing the test skipping will only hide the problem. > Please don't do it here and in the future. > Instead let's figure out the real solution. > Assuming that vfs_getattr was added to btf_allowlist_d_path > for a reason we have to make this introspection place > reliable regardless of compiler inlining decisions. > We can mark it as 'noinline', but that's undesirable. > I suggest we remove it from the allowlist and replace it with > security_inode_getattr. > I think that is a better long term fix. in my case vfs_getattr got inlined in vfs_statx_fd and both of them are defined in fs/stat.c so the idea is that inlining will not happen if the function is defined in another object? or less likely..? we should be safe when it's called from module > While at it I would apply the same critical thinking to other > functions in the allowlist. They might suffer the same issue. > So s/vfs_truncate/security_path_truncate/ and so on? > Things won't work when CONFIG_SECURITY is off, but that is a rare kernel config? > Or add both security_* and vfs_* variants and switch tests to use security_* ? > but it feels fragile to allow inline-able funcs in allowlist. hm, what's the difference between vfs_getattr and security_inode_getattr in this regard? I'd expect compiler could inline it same way as for vfs_getattr jirka
