[PATCH v3 08/10] mm/vmalloc: undo partial mappings inside the mapping functions
From: Hao Ge
Date: Mon Oct 26 2026 - 04:04:21 EST
The vmap entry points can install some PTEs, then fail and leave the
partial mapping behind.
The callers do not agree on who cleans it up. pcpu_map_pages() and
kmsan_ioremap_page_range() roll back what they mapped, while
vm_module_tags_populate() and the __GFP_NOFAIL retry loop in
__vmalloc_area_node() expect a clean range from the mapping function.
For them the leftovers stay mapped, and the next attempt to map the
same range fails, with a BUG() in vmap_pte_range() for huge mappings
and a warning on the small-page path.
After discussing with Suren and Ulad, we decided to put the rollback
into the entry points of the vmap API rather than into every low-level
helper. __vmap_pages_range_noflush() undoes the whole range it was
asked to map when it fails, and vmap_page_range() undoes its range
for the ioremap-style mappings.
The rollback is __vunmap_range_noflush(), which only clears the PTEs.
No TLB flush is needed, nothing has touched the mapping yet.
vmap_pages_range_noflush() also drops the KMSAN metadata of the failed
mapping.
The undo walk skips its cond_resched() when the caller's gfp mask
cannot block: __vmalloc() with GFP_ATOMIC or GFP_NOWAIT can run in
atomic context, where cond_resched() cannot schedule and its
__might_resched() annotation fires on CONFIG_DEBUG_ATOMIC_SLEEP
builds. __vunmap_range_noflush() takes a can_resched argument for
that, which the sleepable callers pass as true.
Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
Suggested-by: Uladyslau Rezki <urezki@xxxxxxxxx>
Signed-off-by: Hao Ge <hao.ge@xxxxxxxxx>
---
include/linux/kmsan.h | 8 +++--
mm/kmsan/hooks.c | 18 ++++++----
mm/kmsan/shadow.c | 7 ++--
mm/vmalloc.c | 78 ++++++++++++++++++++++++++++++-------------
mm/vmalloc.h | 6 ++--
5 files changed, 79 insertions(+), 38 deletions(-)
diff --git a/include/linux/kmsan.h b/include/linux/kmsan.h
index 7da9fd506b39..0016c032d1e7 100644
--- a/include/linux/kmsan.h
+++ b/include/linux/kmsan.h
@@ -150,11 +150,14 @@ int __must_check kmsan_vmap_pages_range_noflush(unsigned long start,
* kmsan_vunmap_kernel_range_noflush() - Notify KMSAN about a vunmap.
* @start: start of vunmapped range.
* @end: end of vunmapped range.
+ * @can_resched: whether the unmap walk may call cond_resched(); pass
+ * false from atomic context.
*
* KMSAN unmaps the contiguous metadata ranges created by
* kmsan_map_kernel_range_noflush().
*/
-void kmsan_vunmap_range_noflush(unsigned long start, unsigned long end);
+void kmsan_vunmap_range_noflush(unsigned long start, unsigned long end,
+ bool can_resched);
/**
* kmsan_ioremap_page_range() - Notify KMSAN about a ioremap_page_range() call.
@@ -355,7 +358,8 @@ static inline int __must_check kmsan_vmap_pages_range_noflush(
}
static inline void kmsan_vunmap_range_noflush(unsigned long start,
- unsigned long end)
+ unsigned long end,
+ bool can_resched)
{
}
diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c
index 107f66841274..0cd1edaa1120 100644
--- a/mm/kmsan/hooks.c
+++ b/mm/kmsan/hooks.c
@@ -136,13 +136,16 @@ static unsigned long vmalloc_origin(unsigned long addr)
KMSAN_META_ORIGIN);
}
-void kmsan_vunmap_range_noflush(unsigned long start, unsigned long end)
+void kmsan_vunmap_range_noflush(unsigned long start, unsigned long end,
+ bool can_resched)
{
if (!kmsan_enabled)
return;
- __vunmap_range_noflush(vmalloc_shadow(start), vmalloc_shadow(end));
- __vunmap_range_noflush(vmalloc_origin(start), vmalloc_origin(end));
+ __vunmap_range_noflush(vmalloc_shadow(start), vmalloc_shadow(end),
+ can_resched);
+ __vunmap_range_noflush(vmalloc_origin(start), vmalloc_origin(end),
+ can_resched);
flush_cache_vmap(vmalloc_shadow(start), vmalloc_shadow(end));
flush_cache_vmap(vmalloc_origin(start), vmalloc_origin(end));
}
@@ -171,8 +174,9 @@ static void kmsan_iounmap_pages(unsigned long start, unsigned long end)
if (origin)
__free_pages(origin, KMSAN_IOREMAP_META_ORDER);
}
- __vunmap_range_noflush(shadow_start, shadow_end);
- __vunmap_range_noflush(origin_start, origin_end);
+ /* ioremap metadata mappings are always GFP_KERNEL, so resched is safe. */
+ __vunmap_range_noflush(shadow_start, shadow_end, true);
+ __vunmap_range_noflush(origin_start, origin_end, true);
flush_tlb_kernel_range(shadow_start, shadow_end);
flush_tlb_kernel_range(origin_start, origin_end);
}
@@ -207,7 +211,7 @@ int kmsan_ioremap_page_range(unsigned long start, unsigned long end,
mapped = __vmap_pages_range_noflush(
vmalloc_shadow(start + off),
vmalloc_shadow(start + off + PAGE_SIZE), prot, &shadow,
- PAGE_SHIFT);
+ PAGE_SHIFT, gfp_mask);
if (mapped) {
err = mapped;
goto ret;
@@ -217,7 +221,7 @@ int kmsan_ioremap_page_range(unsigned long start, unsigned long end,
mapped = __vmap_pages_range_noflush(
vmalloc_origin(start + off),
vmalloc_origin(start + off + PAGE_SIZE), prot, &origin,
- PAGE_SHIFT);
+ PAGE_SHIFT, gfp_mask);
if (mapped) {
err = mapped;
goto ret;
diff --git a/mm/kmsan/shadow.c b/mm/kmsan/shadow.c
index 2166086d3dc3..452760a333e4 100644
--- a/mm/kmsan/shadow.c
+++ b/mm/kmsan/shadow.c
@@ -247,7 +247,7 @@ int kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end,
origin_end = vmalloc_meta((void *)end, KMSAN_META_ORIGIN);
kmsan_enter_runtime();
mapped = __vmap_pages_range_noflush(shadow_start, shadow_end, prot,
- s_pages, page_shift);
+ s_pages, page_shift, gfp_mask);
kmsan_leave_runtime();
if (mapped) {
err = mapped;
@@ -255,12 +255,13 @@ int kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end,
}
kmsan_enter_runtime();
mapped = __vmap_pages_range_noflush(origin_start, origin_end, prot,
- o_pages, page_shift);
+ o_pages, page_shift, gfp_mask);
kmsan_leave_runtime();
if (mapped) {
/* Undo the shadow mapping set up above. */
kmsan_enter_runtime();
- __vunmap_range_noflush(shadow_start, shadow_end);
+ __vunmap_range_noflush(shadow_start, shadow_end,
+ gfpflags_allow_blocking(gfp_mask));
kmsan_leave_runtime();
err = mapped;
goto ret;
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 96e15d6cfc6d..2b68f7263d53 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -362,8 +362,11 @@ int vmap_page_range(unsigned long addr, unsigned long end,
if (!err)
err = kmsan_ioremap_page_range(addr, end, phys_addr, prot,
ioremap_max_page_shift);
- if (err)
+ if (err) {
+ /* Callers are ioremap and arch setup code, always sleepable. */
+ __vunmap_range_noflush(addr, end, true);
return err;
+ }
flush_cache_vmap(addr, end);
return 0;
@@ -426,7 +429,7 @@ static void vunmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
}
static void vunmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
- pgtbl_mod_mask *mask)
+ pgtbl_mod_mask *mask, bool can_resched)
{
pmd_t *pmd;
unsigned long next;
@@ -448,12 +451,14 @@ static void vunmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
continue;
vunmap_pte_range(pmd, addr, next, mask);
- cond_resched();
+ /* The undo path may run in atomic context. */
+ if (can_resched)
+ cond_resched();
} while (pmd++, addr = next, addr != end);
}
static void vunmap_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
- pgtbl_mod_mask *mask)
+ pgtbl_mod_mask *mask, bool can_resched)
{
pud_t *pud;
unsigned long next;
@@ -473,12 +478,12 @@ static void vunmap_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
}
if (pud_none_or_clear_bad(pud))
continue;
- vunmap_pmd_range(pud, addr, next, mask);
+ vunmap_pmd_range(pud, addr, next, mask, can_resched);
} while (pud++, addr = next, addr != end);
}
static void vunmap_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
- pgtbl_mod_mask *mask)
+ pgtbl_mod_mask *mask, bool can_resched)
{
p4d_t *p4d;
unsigned long next;
@@ -493,7 +498,7 @@ static void vunmap_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
if (p4d_none_or_clear_bad(p4d))
continue;
- vunmap_pud_range(p4d, addr, next, mask);
+ vunmap_pud_range(p4d, addr, next, mask, can_resched);
} while (p4d++, addr = next, addr != end);
}
@@ -509,7 +514,8 @@ static void vunmap_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
*
* This is an internal function only. Do not use outside mm/.
*/
-void __vunmap_range_noflush(unsigned long start, unsigned long end)
+void __vunmap_range_noflush(unsigned long start, unsigned long end,
+ bool can_resched)
{
unsigned long next;
pgd_t *pgd;
@@ -524,7 +530,7 @@ void __vunmap_range_noflush(unsigned long start, unsigned long end)
mask |= PGTBL_PGD_MODIFIED;
if (pgd_none_or_clear_bad(pgd))
continue;
- vunmap_p4d_range(pgd, addr, next, &mask);
+ vunmap_p4d_range(pgd, addr, next, &mask, can_resched);
} while (pgd++, addr = next, addr != end);
if (mask & ARCH_PAGE_TABLE_SYNC_MASK)
@@ -533,8 +539,9 @@ void __vunmap_range_noflush(unsigned long start, unsigned long end)
void vunmap_range_noflush(unsigned long start, unsigned long end)
{
- kmsan_vunmap_range_noflush(start, end);
- __vunmap_range_noflush(start, end);
+ /* The unmap paths are sleepable, keep the resched point. */
+ kmsan_vunmap_range_noflush(start, end, true);
+ __vunmap_range_noflush(start, end, true);
}
/**
@@ -694,12 +701,19 @@ static int vmap_small_pages_range_noflush(unsigned long addr, unsigned long end,
* The caller is responsible for calling flush_cache_vmap() after this
* function returns successfully and before the addresses are accessed.
*
+ * On failure the mapping is torn down before returning, so a retry
+ * sees a clean range. When @gfp_mask cannot block, the teardown
+ * skips cond_resched(), it may run in atomic context.
+ *
* This is an internal function only. Do not use outside mm/.
*/
int __vmap_pages_range_noflush(unsigned long addr, unsigned long end,
- pgprot_t prot, struct page **pages, unsigned int page_shift)
+ pgprot_t prot, struct page **pages, unsigned int page_shift,
+ gfp_t gfp_mask)
{
unsigned int i, nr = (end - addr) >> PAGE_SHIFT;
+ unsigned long start = addr;
+ int err = 0;
if (WARN_ON_ONCE(addr >= end))
return -EINVAL;
@@ -711,22 +725,27 @@ int __vmap_pages_range_noflush(unsigned long addr, unsigned long end,
return -EINVAL;
if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC) ||
- page_shift == PAGE_SHIFT)
- return vmap_small_pages_range_noflush(addr, end, prot, pages);
-
- for (i = 0; i < nr; i += 1U << (page_shift - PAGE_SHIFT)) {
- int err;
-
- err = vmap_range_noflush(addr, addr + (1UL << page_shift),
+ page_shift == PAGE_SHIFT) {
+ err = vmap_small_pages_range_noflush(addr, end, prot, pages);
+ } else {
+ for (i = 0; i < nr; i += 1U << (page_shift - PAGE_SHIFT)) {
+ err = vmap_range_noflush(addr,
+ addr + (1UL << page_shift),
page_to_phys(pages[i]), prot,
page_shift);
- if (err)
- return err;
+ if (err)
+ break;
- addr += 1UL << page_shift;
+ addr += 1UL << page_shift;
+ }
}
- return 0;
+ /* Undo the PTEs installed before the failure. */
+ if (err)
+ __vunmap_range_noflush(start, end,
+ gfpflags_allow_blocking(gfp_mask));
+
+ return err;
}
int vmap_pages_range_noflush(unsigned long addr, unsigned long end,
@@ -738,7 +757,18 @@ int vmap_pages_range_noflush(unsigned long addr, unsigned long end,
if (ret)
return ret;
- return __vmap_pages_range_noflush(addr, end, prot, pages, page_shift);
+
+ ret = __vmap_pages_range_noflush(addr, end, prot, pages, page_shift,
+ gfp_mask);
+ /*
+ * The page tables undo themselves on failure. Tear down the
+ * metadata that was fully set up before the mapping failed.
+ */
+ if (ret)
+ kmsan_vunmap_range_noflush(addr, end,
+ gfpflags_allow_blocking(gfp_mask));
+
+ return ret;
}
static int __vmap_pages_range(unsigned long addr, unsigned long end,
diff --git a/mm/vmalloc.h b/mm/vmalloc.h
index d8372a4f65c4..9ea28845f713 100644
--- a/mm/vmalloc.h
+++ b/mm/vmalloc.h
@@ -40,10 +40,12 @@ void clear_vm_uninitialized_flag(struct vm_struct *vm);
int __must_check __vmap_pages_range_noflush(unsigned long addr,
unsigned long end, pgprot_t prot,
- struct page **pages, unsigned int page_shift);
+ struct page **pages, unsigned int page_shift,
+ gfp_t gfp_mask);
void vunmap_range_noflush(unsigned long start, unsigned long end);
-void __vunmap_range_noflush(unsigned long start, unsigned long end);
+void __vunmap_range_noflush(unsigned long start, unsigned long end,
+ bool can_resched);
#endif /* __MM_VMALLOC_H */
--
2.25.1