Re: [RESEND PATCH v3 2/4] iommu/iova: Avoid double-negatives in magazine helpers
On 2020/12/9 19:39, John Garry wrote: > On 09/12/2020 09:03, Leizhen (ThunderTown) wrote: >> >> >> On 2020/11/17 18:25, John Garry wrote: >>> 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 >>> >>> Mem abort info: >>> ESR = 0x9604 >>> EC = 0x25: DABT (current EL), IL = 32 bits >>> SET = 0, FnV = 0 >>> EA = 0, S1PTW = 0 >>> Data abort info: >>> ISV = 0, ISS = 0x0004 >>> CM = 0, WnR = 0 >>> [] user address but active_mm is swapper >>> Internal error: Oops: 9604 [#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 d421 (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 > > Thanks for checking here... > >>> --- >>> 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(_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(>lock); >>> if (rcache->depot_size < MAX_GLOBAL_MAGS) { >>> - rcache->depot[rcache->depot_size++] = >>> - cpu_rcache->loaded; >>> + if (cpu_rcache->loaded) >> >> Looks like it just needs to change
[RESEND PATCH v3 2/4] iommu/iova: Avoid double-negatives in magazine helpers
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 Mem abort info: ESR = 0x9604 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 Data abort info: ISV = 0, ISS = 0x0004 CM = 0, WnR = 0 [] user address but active_mm is swapper Internal error: Oops: 9604 [#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 d421 (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 --- 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(_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(>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(_rcache->lock, flags); - if (!iova_magazine_empty(cpu_rcache->loaded)) { + if