From: John Garry <john.garry@huawei.com>
To: <robin.murphy@arm.com>, <joro@8bytes.org>, <will@kernel.org>
Cc: linuxarm@huawei.com, linux-kernel@vger.kernel.org,
iommu@lists.linux-foundation.org, xiyou.wangcong@gmail.com
Subject: [RESEND PATCH v3 2/4] iommu/iova: Avoid double-negatives in magazine helpers
Date: Tue, 17 Nov 2020 18:25:32 +0800 [thread overview]
Message-ID: <1605608734-84416-3-git-send-email-john.garry@huawei.com> (raw)
In-Reply-To: <1605608734-84416-1-git-send-email-john.garry@huawei.com>
A similar crash to the following could be observed if initial CPU rcache
magazine allocations fail in init_iova_rcaches():
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
Mem abort info:
ESR = 0x96000004
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
Data abort info:
ISV = 0, ISS = 0x00000004
CM = 0, WnR = 0
[0000000000000000] user address but active_mm is swapper
Internal error: Oops: 96000004 [#1] PREEMPT SMP
Modules linked in:
CPU: 11 PID: 696 Comm: irq/40-hisi_sas Not tainted 5.9.0-rc7-dirty #109
Hardware name: Huawei D06 /D06, BIOS Hisilicon D06 UEFI RC0 - V1.16.01 03/15/2019
Call trace:
free_iova_fast+0xfc/0x280
iommu_dma_free_iova+0x64/0x70
__iommu_dma_unmap+0x9c/0xf8
iommu_dma_unmap_sg+0xa8/0xc8
dma_unmap_sg_attrs+0x28/0x50
cq_thread_v3_hw+0x2dc/0x528
irq_thread_fn+0x2c/0xa0
irq_thread+0x130/0x1e0
kthread+0x154/0x158
ret_from_fork+0x10/0x34
Code: f9400060 f102001f 54000981 d4210000 (f9400043)
---[ end trace 4afcbdfc61b60467 ]---
The issue is that expression !iova_magazine_full(NULL) evaluates true; this
falls over in in __iova_rcache_insert() when we attempt to cache a mag
and cpu_rcache->loaded == NULL:
if (!iova_magazine_full(cpu_rcache->loaded)) {
can_insert = true;
...
if (can_insert)
iova_magazine_push(cpu_rcache->loaded, iova_pfn);
As above, can_insert is evaluated true, which it shouldn't be, and we try
to insert pfns in a NULL mag, which is not safe.
To avoid this, stop using double-negatives, like !iova_magazine_full() and
!iova_magazine_empty(), and use positive tests, like
iova_magazine_has_space() and iova_magazine_has_pfns(), respectively; these
can safely deal with cpu_rcache->{loaded, prev} = NULL.
Signed-off-by: John Garry <john.garry@huawei.com>
---
drivers/iommu/iova.c | 29 +++++++++++++++++------------
1 file changed, 17 insertions(+), 12 deletions(-)
diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index 81b7399dd5e8..1f3f0f8b12e0 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -827,14 +827,18 @@ iova_magazine_free_pfns(struct iova_magazine *mag, struct iova_domain *iovad)
mag->size = 0;
}
-static bool iova_magazine_full(struct iova_magazine *mag)
+static bool iova_magazine_has_space(struct iova_magazine *mag)
{
- return (mag && mag->size == IOVA_MAG_SIZE);
+ if (!mag)
+ return false;
+ return mag->size < IOVA_MAG_SIZE;
}
-static bool iova_magazine_empty(struct iova_magazine *mag)
+static bool iova_magazine_has_pfns(struct iova_magazine *mag)
{
- return (!mag || mag->size == 0);
+ if (!mag)
+ return false;
+ return mag->size;
}
static unsigned long iova_magazine_pop(struct iova_magazine *mag,
@@ -843,7 +847,7 @@ static unsigned long iova_magazine_pop(struct iova_magazine *mag,
int i;
unsigned long pfn;
- BUG_ON(iova_magazine_empty(mag));
+ BUG_ON(!iova_magazine_has_pfns(mag));
/* Only fall back to the rbtree if we have no suitable pfns at all */
for (i = mag->size - 1; mag->pfns[i] > limit_pfn; i--)
@@ -859,7 +863,7 @@ static unsigned long iova_magazine_pop(struct iova_magazine *mag,
static void iova_magazine_push(struct iova_magazine *mag, unsigned long pfn)
{
- BUG_ON(iova_magazine_full(mag));
+ BUG_ON(!iova_magazine_has_space(mag));
mag->pfns[mag->size++] = pfn;
}
@@ -905,9 +909,9 @@ static bool __iova_rcache_insert(struct iova_domain *iovad,
cpu_rcache = raw_cpu_ptr(rcache->cpu_rcaches);
spin_lock_irqsave(&cpu_rcache->lock, flags);
- if (!iova_magazine_full(cpu_rcache->loaded)) {
+ if (iova_magazine_has_space(cpu_rcache->loaded)) {
can_insert = true;
- } else if (!iova_magazine_full(cpu_rcache->prev)) {
+ } else if (iova_magazine_has_space(cpu_rcache->prev)) {
swap(cpu_rcache->prev, cpu_rcache->loaded);
can_insert = true;
} else {
@@ -916,8 +920,9 @@ static bool __iova_rcache_insert(struct iova_domain *iovad,
if (new_mag) {
spin_lock(&rcache->lock);
if (rcache->depot_size < MAX_GLOBAL_MAGS) {
- rcache->depot[rcache->depot_size++] =
- cpu_rcache->loaded;
+ if (cpu_rcache->loaded)
+ rcache->depot[rcache->depot_size++] =
+ cpu_rcache->loaded;
} else {
mag_to_free = cpu_rcache->loaded;
}
@@ -968,9 +973,9 @@ static unsigned long __iova_rcache_get(struct iova_rcache *rcache,
cpu_rcache = raw_cpu_ptr(rcache->cpu_rcaches);
spin_lock_irqsave(&cpu_rcache->lock, flags);
- if (!iova_magazine_empty(cpu_rcache->loaded)) {
+ if (iova_magazine_has_pfns(cpu_rcache->loaded)) {
has_pfn = true;
- } else if (!iova_magazine_empty(cpu_rcache->prev)) {
+ } else if (iova_magazine_has_pfns(cpu_rcache->prev)) {
swap(cpu_rcache->prev, cpu_rcache->loaded);
has_pfn = true;
} else {
--
2.26.2
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next prev parent reply other threads:[~2020-11-17 10:30 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-17 10:25 [RESEND PATCH v3 0/4] iommu/iova: Solve longterm IOVA issue John Garry
2020-11-17 10:25 ` [RESEND PATCH v3 1/4] iommu/iova: Add free_all_cpu_cached_iovas() John Garry
2020-12-09 8:58 ` Leizhen (ThunderTown)
2020-12-09 12:41 ` John Garry
2020-11-17 10:25 ` John Garry [this message]
2020-12-09 9:03 ` [RESEND PATCH v3 2/4] iommu/iova: Avoid double-negatives in magazine helpers Leizhen (ThunderTown)
2020-12-09 11:39 ` John Garry
2020-12-09 12:31 ` Leizhen (ThunderTown)
2020-11-17 10:25 ` [RESEND PATCH v3 3/4] iommu/iova: Flush CPU rcache for when a depot fills John Garry
2020-12-09 9:13 ` Leizhen (ThunderTown)
2020-12-09 11:22 ` John Garry
2020-12-09 12:11 ` Leizhen (ThunderTown)
2020-11-17 10:25 ` [RESEND PATCH v3 4/4] iommu: avoid taking iova_rbtree_lock twice John Garry
2020-12-01 15:35 ` [RESEND PATCH v3 0/4] iommu/iova: Solve longterm IOVA issue John Garry
2020-12-01 21:02 ` Will Deacon
2020-12-02 15:20 ` John Garry
2020-12-01 21:45 ` Will Deacon
2020-12-03 6:04 ` Dmitry Safonov
2020-12-03 14:54 ` John Garry
2021-01-15 11:32 ` John Garry
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