On Sun, Mar 24, 2024 at 12:50 PM Roberto Sassu <roberto.sassu@xxxxxxxxxx> wrote: > > From: Al Viro [mailto:viro@xxxxxxxxxxxxxxxx] On Behalf Of Al Viro > > Sent: Sunday, March 24, 2024 6:47 AM > > On Sun, Mar 24, 2024 at 12:00:15AM -0500, Steve French wrote: > > > Anyone else seeing this kernel crash in do_mknodat (I see it with a > > > simple "mkfifo" on smb3 mount). I started seeing this in 6.9-rc (did > > > not see it in 6.8). I did not see it with the 3/12/23 mainline > > > (early in the 6.9-rc merge Window) but I do see it in the 3/22 build > > > so it looks like the regression was introduced by: > > > > FWIW, successful ->mknod() is allowed to return 0 and unhash > > dentry, rather than bothering with lookups. So commit in question > > is bogus - lack of error does *NOT* mean that you have struct inode > > existing, let alone attached to dentry. That kind of behaviour > > used to be common for network filesystems more than just for ->mknod(), > > the theory being "if somebody wants to look at it, they can bloody > > well pay the cost of lookup after dcache miss". > > > > Said that, the language in D/f/vfs.rst is vague as hell and is very easy > > to misread in direction of "you must instantiate". > > > > Thankfully, there's no counterpart with mkdir - *there* it's not just > > possible, it's inevitable in some cases for e.g. nfs. > > > > What the hell is that hook doing in non-S_IFREG cases, anyway? Move it > > up and be done with it... > > Hi Al > > thanks for the patch. Indeed, it was like that before, when instead of > an LSM hook there was an IMA call. > > However, I thought, since we were promoting it as an LSM hook, > we should be as generic possible, and support more usages than > what was needed for IMA. > > > diff --git a/fs/namei.c b/fs/namei.c > > index ceb9ddf8dfdd..821fe0e3f171 100644 > > --- a/fs/namei.c > > +++ b/fs/namei.c > > @@ -4050,6 +4050,8 @@ static int do_mknodat(int dfd, struct filename *name, umode_t mode, > > case 0: case S_IFREG: > > error = vfs_create(idmap, path.dentry->d_inode, > > dentry, mode, true); > > + if (!error) > > + error = security_path_post_mknod(idmap, dentry); > > Minor issue, security_path_post_mknod() does not return an error. > > Also, please update the description of security_path_post_mknod() to say > that it is not going to be called for non-regular files. > > Hopefully, Paul also agrees with this change. > > Other than that, please add my: > > Reviewed-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx> No objections here for obvious reasons. Acked-by: Paul Moore <paul@xxxxxxxxxxxxxx> -- paul-moore.com
