[PATCH] checkpoint: discard const from struct cred * where appropriate

[PATCH] checkpoint: discard const from struct cred * where appropriate

[Nathan Lynch]

Building the checkpoint tree results in enough build noise that
it's getting easy to miss new warnings added during development:

kernel/cred.c:737: warning: passing argument 2 of 'checkpoint_capabilities' discards qualifiers from pointer target type
checkpoint/process.c:146: warning: assignment discards qualifiers from pointer target type
checkpoint/process.c:147: warning: assignment discards qualifiers from pointer target type
checkpoint/files.c:154: warning: passing argument 2 of 'checkpoint_obj' discards qualifiers from pointer target type

The objhash code would require significant modification to properly
handle const objects, and only struct cred * is causing this kind of
warning, so just insert casts or drop const where it makes sense.

Signed-off-by: Nathan Lynch <ntl-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org>
---
 checkpoint/files.c   |    4 +++-
 checkpoint/process.c |    4 ++--
 kernel/cred.c        |    2 +-
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/checkpoint/files.c b/checkpoint/files.c
index 204055b..8f90c16 100644
--- a/checkpoint/files.c
+++ b/checkpoint/files.c
@@ -146,12 +146,14 @@ static int scan_fds(struct files_struct *files, int **fdtable)
 int checkpoint_file_common(struct ckpt_ctx *ctx, struct file *file,
 			   struct ckpt_hdr_file *h)
 {
+	struct cred *f_cred = (struct cred *)file->f_cred;
+
 	h->f_flags = file->f_flags;
 	h->f_mode = file->f_mode;
 	h->f_pos = file->f_pos;
 	h->f_version = file->f_version;
 
-	h->f_credref = checkpoint_obj(ctx, file->f_cred, CKPT_OBJ_CRED);
+	h->f_credref = checkpoint_obj(ctx, f_cred, CKPT_OBJ_CRED);
 	if (h->f_credref < 0)
 		return h->f_credref;
 
diff --git a/checkpoint/process.c b/checkpoint/process.c
index 40b2580..41566db 100644
--- a/checkpoint/process.c
+++ b/checkpoint/process.c
@@ -143,8 +143,8 @@ static int checkpoint_task_creds(struct ckpt_ctx *ctx, struct task_struct *t)
 	struct ckpt_hdr_task_creds *h;
 	int ret;
 
-	rcred = get_cred(t->real_cred);
-	ecred = get_cred(t->cred);
+	rcred = (struct cred *)get_cred(t->real_cred);
+	ecred = (struct cred *)get_cred(t->cred);
 
 	realcred_ref = checkpoint_obj(ctx, rcred, CKPT_OBJ_CRED);
 	if (realcred_ref < 0) {
diff --git a/kernel/cred.c b/kernel/cred.c
index 27e02ca..9710cae 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -706,7 +706,7 @@ int cred_setfsgid(struct cred *new, gid_t gid, gid_t *old_fsgid)
 }
 
 #ifdef CONFIG_CHECKPOINT
-static int do_checkpoint_cred(struct ckpt_ctx *ctx, const struct cred *cred)
+static int do_checkpoint_cred(struct ckpt_ctx *ctx, struct cred *cred)
 {
 	int ret;
 	int groupinfo_ref, user_ref;
-- 
1.6.0.6

Re: [PATCH] checkpoint: discard const from struct cred * where appropriate

[Oren Laadan]

Nathan Lynch wrote:
> Building the checkpoint tree results in enough build noise that
> it's getting easy to miss new warnings added during development:
> 
> kernel/cred.c:737: warning: passing argument 2 of 'checkpoint_capabilities' discards qualifiers from pointer target type
> checkpoint/process.c:146: warning: assignment discards qualifiers from pointer target type
> checkpoint/process.c:147: warning: assignment discards qualifiers from pointer target type
> checkpoint/files.c:154: warning: passing argument 2 of 'checkpoint_obj' discards qualifiers from pointer target type
> 
> The objhash code would require significant modification to properly
> handle const objects, and only struct cred * is causing this kind of
> warning, so just insert casts or drop const where it makes sense.
> 
> Signed-off-by: Nathan Lynch <ntl-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org>

Looks good to me.

I vaguely recall that Serge had some issue with this approach ?

Oren.

> ---
>  checkpoint/files.c   |    4 +++-
>  checkpoint/process.c |    4 ++--
>  kernel/cred.c        |    2 +-
>  3 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/checkpoint/files.c b/checkpoint/files.c
> index 204055b..8f90c16 100644
> --- a/checkpoint/files.c
> +++ b/checkpoint/files.c
> @@ -146,12 +146,14 @@ static int scan_fds(struct files_struct *files, int **fdtable)
>  int checkpoint_file_common(struct ckpt_ctx *ctx, struct file *file,
>  			   struct ckpt_hdr_file *h)
>  {
> +	struct cred *f_cred = (struct cred *)file->f_cred;
> +
>  	h->f_flags = file->f_flags;
>  	h->f_mode = file->f_mode;
>  	h->f_pos = file->f_pos;
>  	h->f_version = file->f_version;
>  
> -	h->f_credref = checkpoint_obj(ctx, file->f_cred, CKPT_OBJ_CRED);
> +	h->f_credref = checkpoint_obj(ctx, f_cred, CKPT_OBJ_CRED);
>  	if (h->f_credref < 0)
>  		return h->f_credref;
>  
> diff --git a/checkpoint/process.c b/checkpoint/process.c
> index 40b2580..41566db 100644
> --- a/checkpoint/process.c
> +++ b/checkpoint/process.c
> @@ -143,8 +143,8 @@ static int checkpoint_task_creds(struct ckpt_ctx *ctx, struct task_struct *t)
>  	struct ckpt_hdr_task_creds *h;
>  	int ret;
>  
> -	rcred = get_cred(t->real_cred);
> -	ecred = get_cred(t->cred);
> +	rcred = (struct cred *)get_cred(t->real_cred);
> +	ecred = (struct cred *)get_cred(t->cred);
>  
>  	realcred_ref = checkpoint_obj(ctx, rcred, CKPT_OBJ_CRED);
>  	if (realcred_ref < 0) {
> diff --git a/kernel/cred.c b/kernel/cred.c
> index 27e02ca..9710cae 100644
> --- a/kernel/cred.c
> +++ b/kernel/cred.c
> @@ -706,7 +706,7 @@ int cred_setfsgid(struct cred *new, gid_t gid, gid_t *old_fsgid)
>  }
>  
>  #ifdef CONFIG_CHECKPOINT
> -static int do_checkpoint_cred(struct ckpt_ctx *ctx, const struct cred *cred)
> +static int do_checkpoint_cred(struct ckpt_ctx *ctx, struct cred *cred)
>  {
>  	int ret;
>  	int groupinfo_ref, user_ref;

Re: [PATCH] checkpoint: discard const from struct cred * where appropriate

[Serge E. Hallyn]

Quoting Oren Laadan (orenl-RdfvBDnrOixBDgjK7y7TUQ@public.gmane.org):
> 
> 
> Nathan Lynch wrote:
> > Building the checkpoint tree results in enough build noise that
> > it's getting easy to miss new warnings added during development:
> > 
> > kernel/cred.c:737: warning: passing argument 2 of 'checkpoint_capabilities' discards qualifiers from pointer target type
> > checkpoint/process.c:146: warning: assignment discards qualifiers from pointer target type
> > checkpoint/process.c:147: warning: assignment discards qualifiers from pointer target type
> > checkpoint/files.c:154: warning: passing argument 2 of 'checkpoint_obj' discards qualifiers from pointer target type
> > 
> > The objhash code would require significant modification to properly
> > handle const objects, and only struct cred * is causing this kind of
> > warning, so just insert casts or drop const where it makes sense.
> > 
> > Signed-off-by: Nathan Lynch <ntl-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org>
> 
> Looks good to me.
> 
> I vaguely recall that Serge had some issue with this approach ?

I don't.  This might be the best solution, and we do need to shut those
warnings up.  David Howells might have a problem with it though, so he
should be cc:d.

> Oren.
> 
> > ---
> >  checkpoint/files.c   |    4 +++-
> >  checkpoint/process.c |    4 ++--
> >  kernel/cred.c        |    2 +-
> >  3 files changed, 6 insertions(+), 4 deletions(-)
> > 
> > diff --git a/checkpoint/files.c b/checkpoint/files.c
> > index 204055b..8f90c16 100644
> > --- a/checkpoint/files.c
> > +++ b/checkpoint/files.c
> > @@ -146,12 +146,14 @@ static int scan_fds(struct files_struct *files, int **fdtable)
> >  int checkpoint_file_common(struct ckpt_ctx *ctx, struct file *file,
> >  			   struct ckpt_hdr_file *h)
> >  {
> > +	struct cred *f_cred = (struct cred *)file->f_cred;
> > +
> >  	h->f_flags = file->f_flags;
> >  	h->f_mode = file->f_mode;
> >  	h->f_pos = file->f_pos;
> >  	h->f_version = file->f_version;
> >  
> > -	h->f_credref = checkpoint_obj(ctx, file->f_cred, CKPT_OBJ_CRED);
> > +	h->f_credref = checkpoint_obj(ctx, f_cred, CKPT_OBJ_CRED);
> >  	if (h->f_credref < 0)
> >  		return h->f_credref;
> >  
> > diff --git a/checkpoint/process.c b/checkpoint/process.c
> > index 40b2580..41566db 100644
> > --- a/checkpoint/process.c
> > +++ b/checkpoint/process.c
> > @@ -143,8 +143,8 @@ static int checkpoint_task_creds(struct ckpt_ctx *ctx, struct task_struct *t)
> >  	struct ckpt_hdr_task_creds *h;
> >  	int ret;
> >  
> > -	rcred = get_cred(t->real_cred);
> > -	ecred = get_cred(t->cred);
> > +	rcred = (struct cred *)get_cred(t->real_cred);
> > +	ecred = (struct cred *)get_cred(t->cred);
> >  
> >  	realcred_ref = checkpoint_obj(ctx, rcred, CKPT_OBJ_CRED);
> >  	if (realcred_ref < 0) {
> > diff --git a/kernel/cred.c b/kernel/cred.c
> > index 27e02ca..9710cae 100644
> > --- a/kernel/cred.c
> > +++ b/kernel/cred.c
> > @@ -706,7 +706,7 @@ int cred_setfsgid(struct cred *new, gid_t gid, gid_t *old_fsgid)
> >  }
> >  
> >  #ifdef CONFIG_CHECKPOINT
> > -static int do_checkpoint_cred(struct ckpt_ctx *ctx, const struct cred *cred)
> > +static int do_checkpoint_cred(struct ckpt_ctx *ctx, struct cred *cred)
> >  {
> >  	int ret;
> >  	int groupinfo_ref, user_ref;
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> https://lists.linux-foundation.org/mailman/listinfo/containers

Re: [PATCH] checkpoint: discard const from struct cred * where appropriate

[Oren Laadan]

Nathan Lynch wrote:
> Building the checkpoint tree results in enough build noise that
> it's getting easy to miss new warnings added during development:
> 
> kernel/cred.c:737: warning: passing argument 2 of 'checkpoint_capabilities' discards qualifiers from pointer target type
> checkpoint/process.c:146: warning: assignment discards qualifiers from pointer target type
> checkpoint/process.c:147: warning: assignment discards qualifiers from pointer target type
> checkpoint/files.c:154: warning: passing argument 2 of 'checkpoint_obj' discards qualifiers from pointer target type
> 
> The objhash code would require significant modification to properly
> handle const objects, and only struct cred * is causing this kind of
> warning, so just insert casts or drop const where it makes sense.
> 
> Signed-off-by: Nathan Lynch <ntl-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org>

Thanks, applied.

> ---
>  checkpoint/files.c   |    4 +++-
>  checkpoint/process.c |    4 ++--
>  kernel/cred.c        |    2 +-
>  3 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/checkpoint/files.c b/checkpoint/files.c
> index 204055b..8f90c16 100644
> --- a/checkpoint/files.c
> +++ b/checkpoint/files.c
> @@ -146,12 +146,14 @@ static int scan_fds(struct files_struct *files, int **fdtable)
>  int checkpoint_file_common(struct ckpt_ctx *ctx, struct file *file,
>  			   struct ckpt_hdr_file *h)
>  {
> +	struct cred *f_cred = (struct cred *)file->f_cred;
> +
>  	h->f_flags = file->f_flags;
>  	h->f_mode = file->f_mode;
>  	h->f_pos = file->f_pos;
>  	h->f_version = file->f_version;
>  
> -	h->f_credref = checkpoint_obj(ctx, file->f_cred, CKPT_OBJ_CRED);
> +	h->f_credref = checkpoint_obj(ctx, f_cred, CKPT_OBJ_CRED);
>  	if (h->f_credref < 0)
>  		return h->f_credref;
>  
> diff --git a/checkpoint/process.c b/checkpoint/process.c
> index 40b2580..41566db 100644
> --- a/checkpoint/process.c
> +++ b/checkpoint/process.c
> @@ -143,8 +143,8 @@ static int checkpoint_task_creds(struct ckpt_ctx *ctx, struct task_struct *t)
>  	struct ckpt_hdr_task_creds *h;
>  	int ret;
>  
> -	rcred = get_cred(t->real_cred);
> -	ecred = get_cred(t->cred);
> +	rcred = (struct cred *)get_cred(t->real_cred);
> +	ecred = (struct cred *)get_cred(t->cred);
>  
>  	realcred_ref = checkpoint_obj(ctx, rcred, CKPT_OBJ_CRED);
>  	if (realcred_ref < 0) {
> diff --git a/kernel/cred.c b/kernel/cred.c
> index 27e02ca..9710cae 100644
> --- a/kernel/cred.c
> +++ b/kernel/cred.c
> @@ -706,7 +706,7 @@ int cred_setfsgid(struct cred *new, gid_t gid, gid_t *old_fsgid)
>  }
>  
>  #ifdef CONFIG_CHECKPOINT
> -static int do_checkpoint_cred(struct ckpt_ctx *ctx, const struct cred *cred)
> +static int do_checkpoint_cred(struct ckpt_ctx *ctx, struct cred *cred)
>  {
>  	int ret;
>  	int groupinfo_ref, user_ref;