diff mbox series

[-mm,v3] mm/page_isolation: fix potential warning from user

Message ID 20200120163915.1469-1-cai@lca.pw
State New, archived
Headers show
Series [-mm,v3] mm/page_isolation: fix potential warning from user | expand

Commit Message

Qian Cai Jan. 20, 2020, 4:39 p.m. UTC
It makes sense to call the WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE)
from start_isolate_page_range(), but should avoid triggering it from
userspace, i.e, from is_mem_section_removable() because it could crash
the system by a non-root user if warn_on_panic is set.

While at it, simplify the code a bit by removing an unnecessary jump
label.

Suggested-by: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Qian Cai <cai@lca.pw>
---

v3: Drop the page_isolation.c cleanup change.
v2: Improve the commit log.
    Warn for all start_isolate_page_range() users not just offlining.

 mm/page_alloc.c     | 11 ++++-------
 mm/page_isolation.c | 18 +++++++++++-------
 2 files changed, 15 insertions(+), 14 deletions(-)

Comments

David Hildenbrand Jan. 20, 2020, 4:51 p.m. UTC | #1
On 20.01.20 17:39, Qian Cai wrote:
> It makes sense to call the WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE)
> from start_isolate_page_range(), but should avoid triggering it from
> userspace, i.e, from is_mem_section_removable() because it could crash
> the system by a non-root user if warn_on_panic is set.
> 
> While at it, simplify the code a bit by removing an unnecessary jump
> label.
> 
> Suggested-by: Michal Hocko <mhocko@kernel.org>
> Signed-off-by: Qian Cai <cai@lca.pw>
> ---
> 
> v3: Drop the page_isolation.c cleanup change.
> v2: Improve the commit log.
>     Warn for all start_isolate_page_range() users not just offlining.
> 
>  mm/page_alloc.c     | 11 ++++-------
>  mm/page_isolation.c | 18 +++++++++++-------
>  2 files changed, 15 insertions(+), 14 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 621716a25639..3c4eb750a199 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8231,7 +8231,7 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page,
>  		if (is_migrate_cma(migratetype))
>  			return NULL;
>  
> -		goto unmovable;
> +		return page;
>  	}
>  
>  	for (; iter < pageblock_nr_pages; iter++) {
> @@ -8241,7 +8241,7 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page,
>  		page = pfn_to_page(pfn + iter);
>  
>  		if (PageReserved(page))
> -			goto unmovable;
> +			return page;
>  
>  		/*
>  		 * If the zone is movable and we have ruled out all reserved
> @@ -8261,7 +8261,7 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page,
>  			unsigned int skip_pages;
>  
>  			if (!hugepage_migration_supported(page_hstate(head)))
> -				goto unmovable;
> +				return page;
>  
>  			skip_pages = compound_nr(head) - (page - head);
>  			iter += skip_pages - 1;
> @@ -8303,12 +8303,9 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page,
>  		 * is set to both of a memory hole page and a _used_ kernel
>  		 * page at boot.
>  		 */
> -		goto unmovable;
> +		return page;
>  	}
>  	return NULL;
> -unmovable:
> -	WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);
> -	return pfn_to_page(pfn + iter);
>  }
>  
>  #ifdef CONFIG_CONTIG_ALLOC
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index e70586523ca3..a9fd7c740c23 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -54,14 +54,18 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_
>  
>  out:
>  	spin_unlock_irqrestore(&zone->lock, flags);
> -	if (!ret)
> +	if (!ret) {
>  		drain_all_pages(zone);
> -	else if ((isol_flags & REPORT_FAILURE) && unmovable)
> -		/*
> -		 * printk() with zone->lock held will guarantee to trigger a
> -		 * lockdep splat, so defer it here.
> -		 */
> -		dump_page(unmovable, "unmovable page");
> +	} else {
> +		WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);
> +
> +		if ((isol_flags & REPORT_FAILURE) && unmovable)
> +			/*
> +			 * printk() with zone->lock held will likely trigger a
> +			 * lockdep splat, so defer it here.
> +			 */
> +			dump_page(unmovable, "unmovable page");
> +	}
>  
>  	return ret;
>  }
> 

Thanks!

Reviewed-by: David Hildenbrand <david@redhat.com>
Michal Hocko Jan. 20, 2020, 5:16 p.m. UTC | #2
On Mon 20-01-20 11:39:15, Qian Cai wrote:
> It makes sense to call the WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE)
> from start_isolate_page_range(), but should avoid triggering it from
> userspace, i.e, from is_mem_section_removable() because it could crash
> the system by a non-root user if warn_on_panic is set.
> 
> While at it, simplify the code a bit by removing an unnecessary jump
> label.
> 
> Suggested-by: Michal Hocko <mhocko@kernel.org>
> Signed-off-by: Qian Cai <cai@lca.pw>

Acked-by: Michal Hocko <mhocko@suse.com>

Thanks!

> ---
> 
> v3: Drop the page_isolation.c cleanup change.
> v2: Improve the commit log.
>     Warn for all start_isolate_page_range() users not just offlining.
> 
>  mm/page_alloc.c     | 11 ++++-------
>  mm/page_isolation.c | 18 +++++++++++-------
>  2 files changed, 15 insertions(+), 14 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 621716a25639..3c4eb750a199 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8231,7 +8231,7 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page,
>  		if (is_migrate_cma(migratetype))
>  			return NULL;
>  
> -		goto unmovable;
> +		return page;
>  	}
>  
>  	for (; iter < pageblock_nr_pages; iter++) {
> @@ -8241,7 +8241,7 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page,
>  		page = pfn_to_page(pfn + iter);
>  
>  		if (PageReserved(page))
> -			goto unmovable;
> +			return page;
>  
>  		/*
>  		 * If the zone is movable and we have ruled out all reserved
> @@ -8261,7 +8261,7 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page,
>  			unsigned int skip_pages;
>  
>  			if (!hugepage_migration_supported(page_hstate(head)))
> -				goto unmovable;
> +				return page;
>  
>  			skip_pages = compound_nr(head) - (page - head);
>  			iter += skip_pages - 1;
> @@ -8303,12 +8303,9 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page,
>  		 * is set to both of a memory hole page and a _used_ kernel
>  		 * page at boot.
>  		 */
> -		goto unmovable;
> +		return page;
>  	}
>  	return NULL;
> -unmovable:
> -	WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);
> -	return pfn_to_page(pfn + iter);
>  }
>  
>  #ifdef CONFIG_CONTIG_ALLOC
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index e70586523ca3..a9fd7c740c23 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -54,14 +54,18 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_
>  
>  out:
>  	spin_unlock_irqrestore(&zone->lock, flags);
> -	if (!ret)
> +	if (!ret) {
>  		drain_all_pages(zone);
> -	else if ((isol_flags & REPORT_FAILURE) && unmovable)
> -		/*
> -		 * printk() with zone->lock held will guarantee to trigger a
> -		 * lockdep splat, so defer it here.
> -		 */
> -		dump_page(unmovable, "unmovable page");
> +	} else {
> +		WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);
> +
> +		if ((isol_flags & REPORT_FAILURE) && unmovable)
> +			/*
> +			 * printk() with zone->lock held will likely trigger a
> +			 * lockdep splat, so defer it here.
> +			 */
> +			dump_page(unmovable, "unmovable page");
> +	}
>  
>  	return ret;
>  }
> -- 
> 2.21.0 (Apple Git-122.2)
diff mbox series

Patch

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 621716a25639..3c4eb750a199 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8231,7 +8231,7 @@  struct page *has_unmovable_pages(struct zone *zone, struct page *page,
 		if (is_migrate_cma(migratetype))
 			return NULL;
 
-		goto unmovable;
+		return page;
 	}
 
 	for (; iter < pageblock_nr_pages; iter++) {
@@ -8241,7 +8241,7 @@  struct page *has_unmovable_pages(struct zone *zone, struct page *page,
 		page = pfn_to_page(pfn + iter);
 
 		if (PageReserved(page))
-			goto unmovable;
+			return page;
 
 		/*
 		 * If the zone is movable and we have ruled out all reserved
@@ -8261,7 +8261,7 @@  struct page *has_unmovable_pages(struct zone *zone, struct page *page,
 			unsigned int skip_pages;
 
 			if (!hugepage_migration_supported(page_hstate(head)))
-				goto unmovable;
+				return page;
 
 			skip_pages = compound_nr(head) - (page - head);
 			iter += skip_pages - 1;
@@ -8303,12 +8303,9 @@  struct page *has_unmovable_pages(struct zone *zone, struct page *page,
 		 * is set to both of a memory hole page and a _used_ kernel
 		 * page at boot.
 		 */
-		goto unmovable;
+		return page;
 	}
 	return NULL;
-unmovable:
-	WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);
-	return pfn_to_page(pfn + iter);
 }
 
 #ifdef CONFIG_CONTIG_ALLOC
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index e70586523ca3..a9fd7c740c23 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -54,14 +54,18 @@  static int set_migratetype_isolate(struct page *page, int migratetype, int isol_
 
 out:
 	spin_unlock_irqrestore(&zone->lock, flags);
-	if (!ret)
+	if (!ret) {
 		drain_all_pages(zone);
-	else if ((isol_flags & REPORT_FAILURE) && unmovable)
-		/*
-		 * printk() with zone->lock held will guarantee to trigger a
-		 * lockdep splat, so defer it here.
-		 */
-		dump_page(unmovable, "unmovable page");
+	} else {
+		WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);
+
+		if ((isol_flags & REPORT_FAILURE) && unmovable)
+			/*
+			 * printk() with zone->lock held will likely trigger a
+			 * lockdep splat, so defer it here.
+			 */
+			dump_page(unmovable, "unmovable page");
+	}
 
 	return ret;
 }