| Message ID | 20241101135452.19359-3-erin.shepherd@e43.eu (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | pidfs: implement file handle support | expand |
On Fri, Nov 1, 2024 at 2:55 PM Erin Shepherd <erin.shepherd@e43.eu> wrote: > > On 64-bit platforms, userspace can read the pidfd's inode in order to > get a never-repeated PID identifier. On 32-bit platforms this identifier > is not exposed, as inodes are limited to 32 bits. Instead expose the > identifier via export_fh, which makes it available to userspace via > name_to_handle_at > > Signed-off-by: Erin Shepherd <erin.shepherd@e43.eu> Reviewed-by: Amir Goldstein <amir73il@gmail.com> > --- > fs/pidfs.c | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) > > diff --git a/fs/pidfs.c b/fs/pidfs.c > index 80675b6bf884..c8e7e9011550 100644 > --- a/fs/pidfs.c > +++ b/fs/pidfs.c > @@ -1,5 +1,6 @@ > // SPDX-License-Identifier: GPL-2.0 > #include <linux/anon_inodes.h> > +#include <linux/exportfs.h> > #include <linux/file.h> > #include <linux/fs.h> > #include <linux/magic.h> > @@ -347,6 +348,25 @@ static const struct dentry_operations pidfs_dentry_operations = { > .d_prune = stashed_dentry_prune, > }; > > +static int pidfs_encode_fh(struct inode *inode, __u32 *fh, int *max_len, > + struct inode *parent) > +{ > + struct pid *pid = inode->i_private; > + > + if (*max_len < 2) { > + *max_len = 2; > + return FILEID_INVALID; > + } > + > + *max_len = 2; > + *(u64 *)fh = pid->ino; > + return FILEID_KERNFS; > +} > + > +static const struct export_operations pidfs_export_operations = { > + .encode_fh = pidfs_encode_fh, > +}; > + > static int pidfs_init_inode(struct inode *inode, void *data) > { > inode->i_private = data; > @@ -382,6 +402,7 @@ static int pidfs_init_fs_context(struct fs_context *fc) > return -ENOMEM; > > ctx->ops = &pidfs_sops; > + ctx->eops = &pidfs_export_operations; > ctx->dops = &pidfs_dentry_operations; > fc->s_fs_info = (void *)&pidfs_stashed_ops; > return 0; > -- > 2.46.1 > >
diff --git a/fs/pidfs.c b/fs/pidfs.c index 80675b6bf884..c8e7e9011550 100644 --- a/fs/pidfs.c +++ b/fs/pidfs.c @@ -1,5 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 #include <linux/anon_inodes.h> +#include <linux/exportfs.h> #include <linux/file.h> #include <linux/fs.h> #include <linux/magic.h> @@ -347,6 +348,25 @@ static const struct dentry_operations pidfs_dentry_operations = { .d_prune = stashed_dentry_prune, }; +static int pidfs_encode_fh(struct inode *inode, __u32 *fh, int *max_len, + struct inode *parent) +{ + struct pid *pid = inode->i_private; + + if (*max_len < 2) { + *max_len = 2; + return FILEID_INVALID; + } + + *max_len = 2; + *(u64 *)fh = pid->ino; + return FILEID_KERNFS; +} + +static const struct export_operations pidfs_export_operations = { + .encode_fh = pidfs_encode_fh, +}; + static int pidfs_init_inode(struct inode *inode, void *data) { inode->i_private = data; @@ -382,6 +402,7 @@ static int pidfs_init_fs_context(struct fs_context *fc) return -ENOMEM; ctx->ops = &pidfs_sops; + ctx->eops = &pidfs_export_operations; ctx->dops = &pidfs_dentry_operations; fc->s_fs_info = (void *)&pidfs_stashed_ops; return 0;
On 64-bit platforms, userspace can read the pidfd's inode in order to get a never-repeated PID identifier. On 32-bit platforms this identifier is not exposed, as inodes are limited to 32 bits. Instead expose the identifier via export_fh, which makes it available to userspace via name_to_handle_at Signed-off-by: Erin Shepherd <erin.shepherd@e43.eu> --- fs/pidfs.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+)