Currently, kasan_free_nondeferred_pages()->kasan_free_pages() is called
after debug_pagealloc_unmap_pages(). This causes a crash when
debug_pagealloc is enabled, as HW_TAGS KASAN can't set tags on an
unmapped page.
This patch puts kasan_free_nondeferred_pages() before
debug_pagealloc_unmap_pages() and arch_free_page(), which can also make
the page unavailable.
Fixes: 94ab5b61ee16 ("kasan, arm64: enable CONFIG_KASAN_HW_TAGS")
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrey Konovalov <andreyknvl(a)google.com>
---
Changes v1->v2:
- Move kasan_free_nondeferred_pages() before arch_free_page().
---
mm/page_alloc.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 969e7012fce0..0efb07b5907c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1304,6 +1304,12 @@ static __always_inline bool free_pages_prepare(struct page *page,
kernel_poison_pages(page, 1 << order);
+ /*
+ * With hardware tag-based KASAN, memory tags must be set before the
+ * page becomes unavailable via debug_pagealloc or arch_free_page.
+ */
+ kasan_free_nondeferred_pages(page, order, fpi_flags);
+
/*
* arch_free_page() can make the page's contents inaccessible. s390
* does this. So nothing which can access the page's contents should
@@ -1313,8 +1319,6 @@ static __always_inline bool free_pages_prepare(struct page *page,
debug_pagealloc_unmap_pages(page, 1 << order);
- kasan_free_nondeferred_pages(page, order, fpi_flags);
-
return true;
}
--
2.30.1.766.gb4fecdf3b7-goog
Currently, kasan_free_nondeferred_pages()->kasan_free_pages() is called
after debug_pagealloc_unmap_pages(). This causes a crash when
debug_pagealloc is enabled, as HW_TAGS KASAN can't set tags on an
unmapped page.
This patch puts kasan_free_nondeferred_pages() before
debug_pagealloc_unmap_pages() and arch_free_page(), which can also make
the page unavailable.
Fixes: 94ab5b61ee16 ("kasan, arm64: enable CONFIG_KASAN_HW_TAGS")
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrey Konovalov <andreyknvl(a)google.com>
---
Changes v2->v3:
- Rebase onto mainline.
---
mm/page_alloc.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3e4b29ee2b1e..c89ee1ba7034 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1281,6 +1281,12 @@ static __always_inline bool free_pages_prepare(struct page *page,
kernel_poison_pages(page, 1 << order);
+ /*
+ * With hardware tag-based KASAN, memory tags must be set before the
+ * page becomes unavailable via debug_pagealloc or arch_free_page.
+ */
+ kasan_free_nondeferred_pages(page, order);
+
/*
* arch_free_page() can make the page's contents inaccessible. s390
* does this. So nothing which can access the page's contents should
@@ -1290,8 +1296,6 @@ static __always_inline bool free_pages_prepare(struct page *page,
debug_pagealloc_unmap_pages(page, 1 << order);
- kasan_free_nondeferred_pages(page, order);
-
return true;
}
--
2.30.1.766.gb4fecdf3b7-goog
The patch titled
Subject: kasan, mm: fix crash with HW_TAGS and DEBUG_PAGEALLOC
has been added to the -mm tree. Its filename is
kasan-mm-fix-crash-with-hw_tags-and-debug_pagealloc.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/kasan-mm-fix-crash-with-hw_tags-a…
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/kasan-mm-fix-crash-with-hw_tags-a…
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Andrey Konovalov <andreyknvl(a)google.com>
Subject: kasan, mm: fix crash with HW_TAGS and DEBUG_PAGEALLOC
Currently, kasan_free_nondeferred_pages()->kasan_free_pages() is called
after debug_pagealloc_unmap_pages(). This causes a crash when
debug_pagealloc is enabled, as HW_TAGS KASAN can't set tags on an
unmapped page.
This patch puts kasan_free_nondeferred_pages() before
debug_pagealloc_unmap_pages() and arch_free_page(), which can also make
the page unavailable.
Link: https://lkml.kernel.org/r/24cd7db274090f0e5bc3adcdc7399243668e3171.16149873…
Fixes: 94ab5b61ee16 ("kasan, arm64: enable CONFIG_KASAN_HW_TAGS")
Signed-off-by: Andrey Konovalov <andreyknvl(a)google.com>
Cc: Catalin Marinas <catalin.marinas(a)arm.com>
Cc: Will Deacon <will.deacon(a)arm.com>
Cc: Vincenzo Frascino <vincenzo.frascino(a)arm.com>
Cc: Dmitry Vyukov <dvyukov(a)google.com>
Cc: Andrey Ryabinin <aryabinin(a)virtuozzo.com>
Cc: Alexander Potapenko <glider(a)google.com>
Cc: Marco Elver <elver(a)google.com>
Cc: Peter Collingbourne <pcc(a)google.com>
Cc: Evgenii Stepanov <eugenis(a)google.com>
Cc: Branislav Rankov <Branislav.Rankov(a)arm.com>
Cc: Kevin Brodsky <kevin.brodsky(a)arm.com>
Cc: Christoph Hellwig <hch(a)infradead.org>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
mm/page_alloc.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
--- a/mm/page_alloc.c~kasan-mm-fix-crash-with-hw_tags-and-debug_pagealloc
+++ a/mm/page_alloc.c
@@ -1282,6 +1282,12 @@ static __always_inline bool free_pages_p
kernel_poison_pages(page, 1 << order);
/*
+ * With hardware tag-based KASAN, memory tags must be set before the
+ * page becomes unavailable via debug_pagealloc or arch_free_page.
+ */
+ kasan_free_nondeferred_pages(page, order);
+
+ /*
* arch_free_page() can make the page's contents inaccessible. s390
* does this. So nothing which can access the page's contents should
* happen after this.
@@ -1290,8 +1296,6 @@ static __always_inline bool free_pages_p
debug_pagealloc_unmap_pages(page, 1 << order);
- kasan_free_nondeferred_pages(page, order);
-
return true;
}
_
Patches currently in -mm which might be from andreyknvl(a)google.com are
kasan-mm-fix-crash-with-hw_tags-and-debug_pagealloc.patch
While Kepler does technically support 256x256 cursors, it turns out that
in order for us to use these correctly we need to make sure that the cursor
plane uses a ctxdma that is set to use small (4K)/large (128K) pages -
whichever is applicable to the given cursor surface.
Right now however, we share the main kmsVramCtxDma that is used for all but
the ovly plane which defaults to small pages - resulting in artifacts when
we use 256x256 cursor surfaces. So until we teach nouveau to use a separate
ctxdma for the cursor, let's just stop advertising 256x256 cursors by
default - which should fix the issues that users were seeing.
Coincidentally - this is also why small ovlys don't work on Kepler: the
ctxdma we use for ovlys is set to large pages.
Changes since v2:
* Fix comments and patch description
Signed-off-by: Lyude Paul <lyude(a)redhat.com>
Fixes: d3b2f0f7921c ("drm/nouveau/kms/nv50-: Report max cursor size to userspace")
Cc: <stable(a)vger.kernel.org> # v5.11+
---
drivers/gpu/drm/nouveau/dispnv50/disp.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
index 196612addfd6..d92cf9e17ac3 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
@@ -2693,9 +2693,19 @@ nv50_display_create(struct drm_device *dev)
else
nouveau_display(dev)->format_modifiers = disp50xx_modifiers;
- if (disp->disp->object.oclass >= GK104_DISP) {
+ /* FIXME: 256x256 cursors are supported on Kepler, however unlike Maxwell and later
+ * generations Kepler requires that we specify the page type, small (4K) or large (128K),
+ * correctly for the ctxdma being used on curs/ovly. We currently share a ctxdma across all
+ * display planes (except ovly) that defaults to small pages, which results in artifacting
+ * on 256x256 cursors. Until we teach nouveau to create an appropriate ctxdma for the cursor
+ * fb in use, simply avoid advertising support for 256x256 cursors.
+ */
+ if (disp->disp->object.oclass >= GM107_DISP) {
dev->mode_config.cursor_width = 256;
dev->mode_config.cursor_height = 256;
+ } else if (disp->disp->object.oclass >= GK104_DISP) {
+ dev->mode_config.cursor_width = 128;
+ dev->mode_config.cursor_height = 128;
} else {
dev->mode_config.cursor_width = 64;
dev->mode_config.cursor_height = 64;
--
2.29.2
process_madvise currently requires ptrace attach capability.
PTRACE_MODE_ATTACH gives one process complete control over another
process. It effectively removes the security boundary between the
two processes (in one direction). Granting ptrace attach capability
even to a system process is considered dangerous since it creates an
attack surface. This severely limits the usage of this API.
The operations process_madvise can perform do not affect the correctness
of the operation of the target process; they only affect where the data
is physically located (and therefore, how fast it can be accessed).
What we want is the ability for one process to influence another process
in order to optimize performance across the entire system while leaving
the security boundary intact.
Replace PTRACE_MODE_ATTACH with a combination of PTRACE_MODE_READ
and CAP_SYS_NICE. PTRACE_MODE_READ to prevent leaking ASLR metadata
and CAP_SYS_NICE for influencing process performance.
Cc: stable(a)vger.kernel.org # 5.10+
Signed-off-by: Suren Baghdasaryan <surenb(a)google.com>
Reviewed-by: Kees Cook <keescook(a)chromium.org>
Acked-by: Minchan Kim <minchan(a)kernel.org>
Acked-by: David Rientjes <rientjes(a)google.com>
---
changes in v3
- Added Reviewed-by: Kees Cook <keescook(a)chromium.org>
- Created man page for process_madvise per Andrew's request: https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/commit/?id=a144…
- cc'ed stable(a)vger.kernel.org # 5.10+ per Andrew's request
- cc'ed linux-security-module(a)vger.kernel.org per James Morris's request
mm/madvise.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/mm/madvise.c b/mm/madvise.c
index df692d2e35d4..01fef79ac761 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1198,12 +1198,22 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
goto release_task;
}
- mm = mm_access(task, PTRACE_MODE_ATTACH_FSCREDS);
+ /* Require PTRACE_MODE_READ to avoid leaking ASLR metadata. */
+ mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
if (IS_ERR_OR_NULL(mm)) {
ret = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
goto release_task;
}
+ /*
+ * Require CAP_SYS_NICE for influencing process performance. Note that
+ * only non-destructive hints are currently supported.
+ */
+ if (!capable(CAP_SYS_NICE)) {
+ ret = -EPERM;
+ goto release_mm;
+ }
+
total_len = iov_iter_count(&iter);
while (iov_iter_count(&iter)) {
@@ -1218,6 +1228,7 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
if (ret == 0)
ret = total_len - iov_iter_count(&iter);
+release_mm:
mmput(mm);
release_task:
put_task_struct(task);
--
2.30.1.766.gb4fecdf3b7-goog