Messages in this thread | | | Date | Fri, 24 Sep 2021 02:56:00 +0000 | From | Al Viro <> | Subject | Re: [PATCH net-next] net: socket: integrate sockfd_lookup() and sockfd_lookup_light() |
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On Wed, Sep 22, 2021 at 02:31:06PM +0800, Yajun Deng wrote:
> -#define sockfd_put(sock) fput(sock->file) > int net_ratelimit(void); > +#define sockfd_put(sock) \ > +do { \ > + struct fd *fd = (struct fd *)&sock->file; \
Have you even bothered to take a look at struct fd declaration? Or struct socket one, for that matter... What we have there is ... struct file *file; struct sock *sk; ...
You are taking the address of 'file' field. And treat it as a pointer to a structure consisting of struct file * and unsigned int.
> + \ > + if (fd->flags & FDPUT_FPUT) \
... so that would take first 4 bytes in the memory occupied by 'sk' field of struct socket and check if bit 0 is set.
And what significance would that bit have, pray tell? On little-endian architectures it's going to be the least significant bit in the first byte in 'sk' field. I.e. there you are testing if the contents of 'sk' (a pointer to struct sock) happens to be odd. It won't be. The same goes for 32bit big-endian - there you will be checking the least significant bit of the 4th byte of 'sk', which again is asking 'is the pointer stored there odd for some reason?'
On 64bit big-endian you are checking if the bit 32 of the address of object sock->sk points to is set. And the answer to that is "hell knows and how could that possibly be relevant to anything?"
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