There are cases when we try to pin a folio but discover that it has
not been faulted-in. So, we try to allocate it in memfd_alloc_folio()
but there is a chance that we might encounter a crash/failure
(VM_BUG_ON(!h->resv_huge_pages)) if there are no active reservations
at that instant. This issue was reported by syzbot:
kernel BUG at mm/hugetlb.c:2403!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5315 Comm: syz.0.0 Not tainted
6.13.0-rc5-syzkaller-00161-g63676eefb7a0 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:alloc_hugetlb_folio_reserve+0xbc/0xc0 mm/hugetlb.c:2403
Code: 1f eb 05 e8 56 18 a0 ff 48 c7 c7 40 56 61 8e e8 ba 21 cc 09 4c 89
f0 5b 41 5c 41 5e 41 5f 5d c3 cc cc cc cc e8 35 18 a0 ff 90 <0f> 0b 66
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f
RSP: 0018:ffffc9000d3d77f8 EFLAGS: 00010087
RAX: ffffffff81ff6beb RBX: 0000000000000000 RCX: 0000000000100000
RDX: ffffc9000e51a000 RSI: 00000000000003ec RDI: 00000000000003ed
RBP: 1ffffffff34810d9 R08: ffffffff81ff6ba3 R09: 1ffffd4000093005
R10: dffffc0000000000 R11: fffff94000093006 R12: dffffc0000000000
R13: dffffc0000000000 R14: ffffea0000498000 R15: ffffffff9a4086c8
FS: 00007f77ac12e6c0(0000) GS:ffff88801fc00000(0000)
knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f77ab54b170 CR3: 0000000040b70000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
memfd_alloc_folio+0x1bd/0x370 mm/memfd.c:88
memfd_pin_folios+0xf10/0x1570 mm/gup.c:3750
udmabuf_pin_folios drivers/dma-buf/udmabuf.c:346 [inline]
udmabuf_create+0x70e/0x10c0 drivers/dma-buf/udmabuf.c:443
udmabuf_ioctl_create drivers/dma-buf/udmabuf.c:495 [inline]
udmabuf_ioctl+0x301/0x4e0 drivers/dma-buf/udmabuf.c:526
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:906 [inline]
__se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Therefore, to avoid this situation and fix this issue, we just need
to make a reservation (by calling hugetlb_reserve_pages()) before
we try to allocate the folio. This will ensure that we are properly
doing region/subpool accounting associated with our allocation.
While at it, move subpool_inode() into hugetlb header and also
replace the VM_BUG_ON() with WARN_ON_ONCE() as there is no need to
crash the system in this scenario and instead we could just warn
and fail the allocation.
Fixes: 26a8ea80929c ("mm/hugetlb: fix memfd_pin_folios resv_huge_pages leak")
Reported-by: syzbot+a504cb5bae4fe117ba94@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@xxxxxxxxx>
Cc: Steve Sistare <steven.sistare@xxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/hugetlb.h | 5 +++++
mm/hugetlb.c | 14 ++++++--------
mm/memfd.c | 14 +++++++++++---
3 files changed, 22 insertions(+), 11 deletions(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index ae4fe8615bb6..38c580548564 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -712,6 +712,11 @@ extern unsigned int default_hstate_idx;
#define default_hstate (hstates[default_hstate_idx])
+static inline struct hugepage_subpool *subpool_inode(struct inode *inode)
+{
+ return HUGETLBFS_SB(inode->i_sb)->spool;
+}
+
static inline struct hugepage_subpool *hugetlb_folio_subpool(struct folio *folio)
{
return folio->_hugetlb_subpool;
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index c498874a7170..ef948f56b864 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -251,11 +251,6 @@ static long hugepage_subpool_put_pages(struct hugepage_subpool *spool,
return ret;
}
-static inline struct hugepage_subpool *subpool_inode(struct inode *inode)
-{
- return HUGETLBFS_SB(inode->i_sb)->spool;
-}
-
static inline struct hugepage_subpool *subpool_vma(struct vm_area_struct *vma)
{
return subpool_inode(file_inode(vma->vm_file));
@@ -2397,12 +2392,15 @@ struct folio *alloc_hugetlb_folio_reserve(struct hstate *h, int preferred_nid,
struct folio *folio;
spin_lock_irq(&hugetlb_lock);
+ if (WARN_ON_ONCE(!h->resv_huge_pages)) {
+ spin_unlock_irq(&hugetlb_lock);
+ return NULL;
+ }
+
folio = dequeue_hugetlb_folio_nodemask(h, gfp_mask, preferred_nid,
nmask);
- if (folio) {
- VM_BUG_ON(!h->resv_huge_pages);
+ if (folio)
h->resv_huge_pages--;
- }
spin_unlock_irq(&hugetlb_lock);
return folio;
diff --git a/mm/memfd.c b/mm/memfd.c
index 35a370d75c9a..0d128c44fb78 100644
--- a/mm/memfd.c
+++ b/mm/memfd.c
@@ -70,7 +70,7 @@ struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx)
#ifdef CONFIG_HUGETLB_PAGE
struct folio *folio;
gfp_t gfp_mask;
- int err;
+ int err = -ENOMEM;
if (is_file_hugepages(memfd)) {
/*
@@ -79,12 +79,16 @@ struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx)
* alloc from. Also, the folio will be pinned for an indefinite
* amount of time, so it is not expected to be migrated away.
*/
+ struct inode *inode = file_inode(memfd);
struct hstate *h = hstate_file(memfd);
gfp_mask = htlb_alloc_mask(h);
gfp_mask &= ~(__GFP_HIGHMEM | __GFP_MOVABLE);
idx >>= huge_page_order(h);
+ if (!hugetlb_reserve_pages(inode, idx, idx + 1, NULL, 0))
+ return ERR_PTR(err);
+
folio = alloc_hugetlb_folio_reserve(h,
numa_node_id(),
NULL,
@@ -95,12 +99,16 @@ struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx)
idx);
if (err) {
folio_put(folio);
- return ERR_PTR(err);
+ goto err;
}
+
+ hugetlb_set_folio_subpool(folio, subpool_inode(inode));
folio_unlock(folio);
return folio;
}
- return ERR_PTR(-ENOMEM);
+err:
+ hugetlb_unreserve_pages(inode, idx, idx + 1, 0);
