Linaro-mm-sig December 2025

linaro-mm-sig@lists.linaro.org

56 participants
44 discussions

Re: [PATCH 1/2] dma-buf: Add __dma_fence_is_signaled()

by kernel test robot

Hello, kernel test robot noticed "Oops:general_protection_fault,probably_for_non-canonical_address#:#[##]SMP_KASAN_PTI" on: commit: 142f20971642be40507d3a0bc94e905e251db81a ("[PATCH 1/2] dma-buf: Add __dma_fence_is_signaled()") url: https://github.com/intel-lab-lkp/linux/commits/Philipp-Stanner/dma-buf-dma-… base: git://linuxtv.org/sailus/media_tree.git master patch link: https://lore.kernel.org/all/20251125104443.82974-2-phasta@kernel.org/ patch subject: [PATCH 1/2] dma-buf: Add __dma_fence_is_signaled() in testcase: lkvs version: lkvs-x86_64-6505b18-1_20251124 with following parameters: test: rapl-client config: x86_64-rhel-9.4-func compiler: gcc-14 test machine: 4 threads Intel(R) Core(TM) i5-6500 CPU @ 3.20GHz (Skylake) with 32G memory (please refer to attached dmesg/kmsg for entire log/backtrace) If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags | Reported-by: kernel test robot <oliver.sang(a)intel.com> | Closes: https://lore.kernel.org/oe-lkp/202512092317.8cf778a-lkp@intel.com [ 46.662293][ T179] i915 0000:00:02.0: vgaarb: VGA decodes changed: olddecodes=io+mem,decodes=io+mem:owns=io+mem [ 46.680656][ T40] sd 1:0:0:0: [sda] Preferred minimum I/O size 4096 bytes [ 46.682302][ T59] i915 0000:00:02.0: Direct firmware load for i915/skl_dmc_ver1_27.bin failed with error -2 [ 46.698362][ T59] i915 0000:00:02.0: [drm] Failed to load DMC firmware i915/skl_dmc_ver1_27.bin (-ENOENT). Disabling runtime power management. [ 46.711256][ T59] i915 0000:00:02.0: [drm] DMC firmware homepage: https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git [ 46.725941][ T12] Oops: general protection fault, probably for non-canonical address 0xdffffc01544551ba: 0000 [#1] SMP KASAN PTI [ 46.725953][ T179] ------------[ cut here ]------------ [ 46.737600][ T12] KASAN: probably user-memory-access in range [0x0000000aa22a8dd0-0x0000000aa22a8dd7] [ 46.737612][ T12] CPU: 3 UID: 0 PID: 12 Comm: kworker/u16:0 Tainted: G S I 6.18.0-rc5-00236-g142f20971642 #1 PREEMPT(voluntary) [ 46.742889][ T179] Fence 0000:00:02.0:[i915]:9:2 released with pending signals! [ 46.752212][ T12] Tainted: [S]=CPU_OUT_OF_SPEC, [I]=FIRMWARE_WORKAROUND [ 46.752217][ T12] Hardware name: Dell Inc. OptiPlex 7040/0Y7WYT, BIOS 1.1.1 10/07/2015 [ 46.752220][ T12] Workqueue: i915 __i915_gem_free_work [i915] [ 46.765216][ T179] WARNING: CPU: 0 PID: 179 at drivers/dma-buf/dma-fence.c:555 dma_fence_release (kbuild/src/consumer/drivers/dma-buf/dma-fence.c:555 (discriminator 1)) [ 46.772517][ T12] [ 46.772521][ T12] RIP: 0010:__list_add_valid_or_report (kbuild/src/consumer/lib/list_debug.c:29) [ 46.772528][ T12] Code: 8b 98 fe 48 89 d3 48 85 d2 0f 84 af 8b 98 fe 4c 8d 62 08 48 89 fd 49 89 f5 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 0f 85 b7 00 00 00 4c 39 6b 08 75 43 48 b8 00 00 00 00 All code ======== 0: 8b 98 fe 48 89 d3 mov -0x2c76b702(%rax),%ebx 6: 48 85 d2 test %rdx,%rdx 9: 0f 84 af 8b 98 fe je 0xfffffffffe988bbe f: 4c 8d 62 08 lea 0x8(%rdx),%r12 13: 48 89 fd mov %rdi,%rbp 16: 49 89 f5 mov %rsi,%r13 19: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax 20: fc ff df 23: 4c 89 e2 mov %r12,%rdx 26: 48 c1 ea 03 shr $0x3,%rdx 2a:* 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction 2e: 0f 85 b7 00 00 00 jne 0xeb 34: 4c 39 6b 08 cmp %r13,0x8(%rbx) 38: 75 43 jne 0x7d 3a: 48 rex.W 3b: b8 00 00 00 00 mov $0x0,%eax Code starting with the faulting instruction =========================================== 0: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) 4: 0f 85 b7 00 00 00 jne 0xc1 a: 4c 39 6b 08 cmp %r13,0x8(%rbx) e: 75 43 jne 0x53 10: 48 rex.W 11: b8 00 00 00 00 mov $0x0,%eax [ 46.779267][ T179] Modules linked in: [ 46.787293][ T12] RSP: 0018:ffffc9000010fac8 EFLAGS: 00010003 [ 46.787300][ T12] RAX: dffffc0000000000 RBX: 0000000aa22a8dcf RCX: ffffffff82f5859d [ 46.793179][ T179] platform_profile [ 46.803018][ T12] RDX: 00000001544551ba RSI: ffff88884fde5c90 RDI: ffffc9000010fb50 [ 46.803023][ T12] RBP: ffffc9000010fb50 R08: 0000000000000000 R09: ffffed1109fbcb96 [ 46.803025][ T12] R10: ffff88884fde5cb7 R11: fefefefefefefeff R12: 0000000aa22a8dd7 [ 46.805219][ T179] sd_mod [ 46.811413][ T12] R13: ffff88884fde5c90 R14: ffff88884fde5c90 R15: 0000000aa22a8dcf [ 46.811417][ T12] FS: 0000000000000000(0000) GS:ffff888848e3e000(0000) knlGS:0000000000000000 [ 46.811419][ T12] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 46.830755][ T179] intel_rapl_common [ 46.834463][ T12] CR2: 00007f3bc83ae000 CR3: 0000000868388002 CR4: 00000000003726f0 [ 46.834467][ T12] Call Trace: [ 46.834469][ T12] <TASK> [ 46.840348][ T179] snd_hda_core [ 46.848115][ T12] dma_fence_default_wait (kbuild/src/consumer/include/linux/list.h:158 (discriminator 1) kbuild/src/consumer/include/linux/list.h:177 (discriminator 1) kbuild/src/consumer/drivers/dma-buf/dma-fence.c:800 (discriminator 1)) [ 46.851758][ T179] x86_pkg_temp_thermal [ 46.859527][ T12] ? __pfx_dma_fence_default_wait (kbuild/src/consumer/drivers/dma-buf/dma-fence.c:778) The kernel config and materials to reproduce are available at: https://download.01.org/0day-ci/archive/20251209/202512092317.8cf778a-lkp@i… -- 0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests/wiki

7 months, 2 weeks

[RFC] dma-buf: system_heap: add PTE_CONT for larger contiguous

by gao xu

commit 04c7adb5871a ("dma-buf: system_heap: use larger contiguous mappings instead of per-page mmap") facilitates the use of PTE_CONT. The system_heap allocates pages of order 4 and 8 that meet the alignment requirements for PTE_CONT. enabling PTE_CONT for larger contiguous mappings. After applying this patch, TLB misses are reduced by approximately 5% when opening the camera on Android systems. Signed-off-by: gao xu <gaoxu2(a)honor.com> --- drivers/dma-buf/heaps/system_heap.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c index 4c782fe33..103b06f89 100644 --- a/drivers/dma-buf/heaps/system_heap.c +++ b/drivers/dma-buf/heaps/system_heap.c @@ -202,12 +202,16 @@ static int system_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma) unsigned long n = (sg->length >> PAGE_SHIFT) - pgoff; struct page *page = sg_page(sg) + pgoff; unsigned long size = n << PAGE_SHIFT; + pgprot_t prot = vma->vm_page_prot; if (addr + size > vma->vm_end) size = vma->vm_end - addr; + if (((addr | size) & ~CONT_PTE_MASK) == 0) + prot = __pgprot(pgprot_val(prot) | PTE_CONT); + ret = remap_pfn_range(vma, addr, page_to_pfn(page), - size, vma->vm_page_prot); + size, prot); if (ret) return ret; -- 2.42.0

7 months, 2 weeks

[PATCH v6 2/8] rust: helpers: Add bindings/wrappers for dma_resv_lock

by Lyude Paul

From: Asahi Lina <lina(a)asahilina.net> This is just for basic usage in the DRM shmem abstractions for implied locking, not intended as a full DMA Reservation abstraction yet. Signed-off-by: Asahi Lina <lina(a)asahilina.net> Signed-off-by: Daniel Almeida <daniel.almeida(a)collabora.com> Reviewed-by: Alice Ryhl <aliceryhl(a)google.com> Signed-off-by: Lyude Paul <lyude(a)redhat.com> --- rust/bindings/bindings_helper.h | 1 + rust/helpers/dma-resv.c | 13 +++++++++++++ rust/helpers/helpers.c | 1 + 3 files changed, 15 insertions(+) create mode 100644 rust/helpers/dma-resv.c diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h index 2e43c66635a2c..07f79e125c329 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -48,6 +48,7 @@ #include <linux/cpumask.h> #include <linux/cred.h> #include <linux/debugfs.h> +#include <linux/dma-resv.h> #include <linux/device/faux.h> #include <linux/dma-direction.h> #include <linux/dma-mapping.h> diff --git a/rust/helpers/dma-resv.c b/rust/helpers/dma-resv.c new file mode 100644 index 0000000000000..05501cb814513 --- /dev/null +++ b/rust/helpers/dma-resv.c @@ -0,0 +1,13 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <linux/dma-resv.h> + +int rust_helper_dma_resv_lock(struct dma_resv *obj, struct ww_acquire_ctx *ctx) +{ + return dma_resv_lock(obj, ctx); +} + +void rust_helper_dma_resv_unlock(struct dma_resv *obj) +{ + dma_resv_unlock(obj); +} diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c index 551da6c9b5064..36d40f911345c 100644 --- a/rust/helpers/helpers.c +++ b/rust/helpers/helpers.c @@ -25,6 +25,7 @@ #include "cred.c" #include "device.c" #include "dma.c" +#include "dma-resv.c" #include "drm.c" #include "err.c" #include "irq.c" -- 2.52.0

7 months, 2 weeks

[syzbot] [media?] [dri?] WARNING in dma_buf_vmap

by syzbot

Hello, syzbot found the following issue on: HEAD commit: 1d18101a644e Merge tag 'kernel-6.19-rc1.cred' of git://git.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=13fba192580000 kernel config: https://syzkaller.appspot.com/x/.config?x=a1db0fea040c2a9f dashboard link: https://syzkaller.appspot.com/bug?extid=4317d7108e14e5d56308 compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1055e2b4580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16ddf484580000 Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk… vmlinux: https://storage.googleapis.com/syzbot-assets/98f78b52cccd/vmlinux-1d18101a.… kernel image: https://storage.googleapis.com/syzbot-assets/7a8898061bfb/bzImage-1d18101a.… IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+4317d7108e14e5d56308(a)syzkaller.appspotmail.com Total swap = 124996kB 393083 pages RAM 0 pages HighMem/MovableOnly 184478 pages reserved 0 pages cma reserved ------------[ cut here ]------------ WARNING: CPU: 0 PID: 5488 at drivers/dma-buf/dma-buf.c:1536 dma_buf_vmap+0x306/0x3b0 drivers/dma-buf/dma-buf.c:1536 Modules linked in: CPU: 0 UID: 0 PID: 5488 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:dma_buf_vmap+0x306/0x3b0 drivers/dma-buf/dma-buf.c:1536 Code: 64 05 cc e8 0c 99 d7 fb 90 0f 0b 90 b8 ea ff ff ff eb bc e8 fc 98 d7 fb 90 0f 0b 90 e9 0d fe ff ff e8 ee 98 d7 fb 44 89 f0 90 <0f> 0b 90 49 bd 00 00 00 00 00 fc ff df eb 91 e8 c6 9c 61 05 48 c7 RSP: 0018:ffffc90002bbf3a0 EFLAGS: 00010293 RAX: 00000000fffffff4 RBX: ffff888000e02428 RCX: ffff888000eb4900 RDX: 0000000000000000 RSI: 00000000fffffff4 RDI: 0000000000000000 RBP: ffffc90002bbf450 R08: ffffc90002bbf227 R09: 1ffff92000577e44 R10: dffffc0000000000 R11: fffff52000577e45 R12: ffffffff85ea4500 R13: ffff888000e02430 R14: 00000000fffffff4 R15: 1ffff110001c0485 FS: 0000555591ecc500(0000) GS:ffff88808d722000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000055859af10a08 CR3: 00000000589bb000 CR4: 0000000000352ef0 Call Trace: <TASK> drm_gem_shmem_vmap_locked+0x14c/0x790 drivers/gpu/drm/drm_gem_shmem_helper.c:354 drm_gem_vmap_locked drivers/gpu/drm/drm_gem.c:1279 [inline] drm_gem_vmap+0x10a/0x1d0 drivers/gpu/drm/drm_gem.c:1321 drm_gem_fb_vmap+0xaa/0x8d0 drivers/gpu/drm/drm_gem_framebuffer_helper.c:368 drm_atomic_helper_prepare_planes+0x2d6/0xb60 drivers/gpu/drm/drm_atomic_helper.c:2760 drm_atomic_helper_commit+0x19a/0xb10 drivers/gpu/drm/drm_atomic_helper.c:2189 drm_atomic_commit+0x262/0x2c0 drivers/gpu/drm/drm_atomic.c:1577 drm_atomic_helper_update_plane+0x248/0x3b0 drivers/gpu/drm/drm_atomic_helper.c:3348 drm_mode_cursor_universal drivers/gpu/drm/drm_plane.c:1256 [inline] drm_mode_cursor_common+0xb7e/0x12d0 drivers/gpu/drm/drm_plane.c:1315 drm_mode_cursor_ioctl+0xbf/0x110 drivers/gpu/drm/drm_plane.c:1365 drm_ioctl_kernel+0x2cf/0x390 drivers/gpu/drm/drm_ioctl.c:797 drm_ioctl+0x67f/0xb10 drivers/gpu/drm/drm_ioctl.c:894 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fcd9898f7c9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffe37777948 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fcd98be5fa0 RCX: 00007fcd9898f7c9 RDX: 0000200000000280 RSI: 00000000c01c64a3 RDI: 0000000000000003 RBP: 00007ffe377779a0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002 R13: 00007fcd98be5fa0 R14: 00007fcd98be5fa0 R15: 0000000000000003 </TASK> --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller(a)googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing. If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup

7 months, 2 weeks

[PATCH 1/2] dma-buf: improve sg_table debugging hack v3

by Christian König

This debugging hack is important to enforce the rule that importers should *never* touch the underlying struct page of the exporter. Instead of just mangling the page link create a copy of the sg_table but only copy over the DMA addresses and not the pages. This will cause a NULL pointer de-reference if the importer tries to touch the struct page. Still quite a hack but this at least allows the exporter to properly keeps it's sg_table intact while allowing the DMA-buf maintainer to find and fix misbehaving importers and finally switch over to using a different data structure in the future. v2: improve the hack further by using a wrapper structure and explaining the background a bit more in the commit message. v3: fix some whitespace issues, use sg_assign_page(). Signed-off-by: Christian König <christian.koenig(a)amd.com> Reviewed-by: Michael J. Ruhl <michael.j.ruhl(a)intel.com> (v1) --- drivers/dma-buf/dma-buf.c | 74 +++++++++++++++++++++++++++++++-------- 1 file changed, 60 insertions(+), 14 deletions(-) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 2305bb2cc1f1..944f4103b5cc 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -35,6 +35,12 @@ #include "dma-buf-sysfs-stats.h" +/* Wrapper to hide the sg_table page link from the importer */ +struct dma_buf_sg_table_wrapper { + struct sg_table *original; + struct sg_table wrapper; +}; + static inline int is_dma_buf_file(struct file *); static DEFINE_MUTEX(dmabuf_list_mutex); @@ -828,21 +834,59 @@ void dma_buf_put(struct dma_buf *dmabuf) } EXPORT_SYMBOL_NS_GPL(dma_buf_put, "DMA_BUF"); -static void mangle_sg_table(struct sg_table *sg_table) +static int dma_buf_mangle_sg_table(struct sg_table **sg_table) { -#ifdef CONFIG_DMABUF_DEBUG - int i; - struct scatterlist *sg; - - /* To catch abuse of the underlying struct page by importers mix - * up the bits, but take care to preserve the low SG_ bits to - * not corrupt the sgt. The mixing is undone on unmap - * before passing the sgt back to the exporter. + struct scatterlist *to_sg, *from_sg; + struct sg_table *from = *sg_table; + struct dma_buf_sg_table_wrapper *to; + int i, ret; + + if (!IS_ENABLED(CONFIG_DMABUF_DEBUG)) + return 0; + + /* + * To catch abuse of the underlying struct page by importers copy the + * sg_table without copying the page_link and give only the copy back to + * the importer. */ - for_each_sgtable_sg(sg_table, sg, i) - sg->page_link ^= ~0xffUL; -#endif + to = kzalloc(sizeof(*to), GFP_KERNEL); + if (!to) + return -ENOMEM; + + ret = sg_alloc_table(&to->wrapper, from->nents, GFP_KERNEL); + if (ret) + goto free_to; + + to_sg = to->wrapper.sgl; + for_each_sgtable_dma_sg(from, from_sg, i) { + to_sg->offset = 0; + to_sg->length = 0; + sg_assign_page(to_sg, NULL); + sg_dma_address(to_sg) = sg_dma_address(from_sg); + sg_dma_len(to_sg) = sg_dma_len(from_sg); + to_sg = sg_next(to_sg); + } + to->original = from; + *sg_table = &to->wrapper; + return 0; + +free_to: + kfree(to); + return ret; +} + +static void dma_buf_demangle_sg_table(struct sg_table **sg_table) +{ + struct dma_buf_sg_table_wrapper *copy; + + if (!IS_ENABLED(CONFIG_DMABUF_DEBUG)) + return; + + copy = container_of(*sg_table, typeof(*copy), wrapper); + *sg_table = copy->original; + sg_free_table(&copy->wrapper); + kfree(copy); } static inline bool @@ -1139,7 +1183,9 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach, if (ret < 0) goto error_unmap; } - mangle_sg_table(sg_table); + ret = dma_buf_mangle_sg_table(&sg_table); + if (ret) + goto error_unmap; if (IS_ENABLED(CONFIG_DMA_API_DEBUG)) { struct scatterlist *sg; @@ -1220,7 +1266,7 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach, dma_resv_assert_held(attach->dmabuf->resv); - mangle_sg_table(sg_table); + dma_buf_demangle_sg_table(&sg_table); attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction); if (dma_buf_pin_on_map(attach)) -- 2.43.0

7 months, 2 weeks

Reasonable maximum signaling timeout for dma_fences

by Christian König

Hi everybody, we have documented here https://www.kernel.org/doc/html/latest/driver-api/dma-buf.html#dma-fence-cr… that dma_fence objects must signal in a reasonable amount of time, but at the same time note that drivers might have a different idea of what reasonable means. Recently I realized that this is actually not a good idea. Background is that the wall clock timeout means that for example the OOM killer might actually wait for this timeout to be able to terminate a process and reclaim the memory used. And this is just an example of how general kernel features might depend on that. Some drivers and fence implementations used 10 seconds and that raised complains by end users. So at least amdgpu recently switched to 2 second which triggered an internal discussion about it. This patch set here now adds a define to the dma_fence header which gives 2 seconds as reasonable amount of time. SW-sync is modified to always taint the kernel (since it doesn't has a timeout), VGEM is switched over to the new define and the scheduler gets a warning and taints the kernel if a driver uses a timeout longer than that. I have not much intention of actually committing the patches (maybe except the SW-sync one), but question is if 2 seconds are reasonable? Regards, Christian.

7 months, 2 weeks

[PATCH 1/2] dma-buf: improve sg_table debugging hack v2

by Christian König

This debugging hack is important to enforce the rule that importers should *never* touch the underlying struct page of the exporter. Instead of just mangling the page link create a copy of the sg_table but only copy over the DMA addresses and not the pages. This will cause a NULL pointer de-reference if the importer tries to touch the struct page. Still quite a hack but this at least allows the exporter to properly keeps it's sg_table intact while allowing the DMA-buf maintainer to find and fix misbehaving importers and finally switch over to using a different data structure in the future. v2: improve the hack further by using a wrapper structure and explaining the background a bit more in the commit message. Signed-off-by: Christian König <christian.koenig(a)amd.com> Reviewed-by: Michael J. Ruhl <michael.j.ruhl(a)intel.com> (v1) --- drivers/dma-buf/dma-buf.c | 72 +++++++++++++++++++++++++++++++-------- 1 file changed, 58 insertions(+), 14 deletions(-) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 2305bb2cc1f1..8c4afd360b72 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -35,6 +35,12 @@ #include "dma-buf-sysfs-stats.h" +/* Wrapper to hide the sg_table page link from the importer */ +struct dma_buf_sg_table_wrapper { + struct sg_table *original; + struct sg_table wrapper; +}; + static inline int is_dma_buf_file(struct file *); static DEFINE_MUTEX(dmabuf_list_mutex); @@ -828,21 +834,57 @@ void dma_buf_put(struct dma_buf *dmabuf) } EXPORT_SYMBOL_NS_GPL(dma_buf_put, "DMA_BUF"); -static void mangle_sg_table(struct sg_table *sg_table) +static int dma_buf_mangle_sg_table(struct sg_table **sg_table) { -#ifdef CONFIG_DMABUF_DEBUG - int i; - struct scatterlist *sg; - - /* To catch abuse of the underlying struct page by importers mix - * up the bits, but take care to preserve the low SG_ bits to - * not corrupt the sgt. The mixing is undone on unmap - * before passing the sgt back to the exporter. + struct scatterlist *to_sg, *from_sg; + struct sg_table *from = *sg_table; + struct dma_buf_sg_table_wrapper *to; + int i, ret; + + if (!IS_ENABLED(CONFIG_DMABUF_DEBUG)) + return 0; + + /* + * To catch abuse of the underlying struct page by importers copy the + * sg_table without copying the page_link and give only the copy back to + * the importer. */ - for_each_sgtable_sg(sg_table, sg, i) - sg->page_link ^= ~0xffUL; -#endif + to = kzalloc(sizeof(*to), GFP_KERNEL); + if (!to) + return -ENOMEM; + + ret = sg_alloc_table(&to->wrapper, from->nents, GFP_KERNEL); + if (ret) + goto free_to; + + to_sg = to->wrapper.sgl; + for_each_sgtable_dma_sg(from, from_sg, i) { + sg_set_page(to_sg, NULL, 0, 0); + sg_dma_address(to_sg) = sg_dma_address(from_sg); + sg_dma_len(to_sg) = sg_dma_len(from_sg); + to_sg = sg_next(to_sg); + } + to->original = from; + *sg_table = &to->wrapper; + return 0; + +free_to: + kfree(to); + return ret; +} + +static void dma_buf_demangle_sg_table(struct sg_table **sg_table) +{ + struct dma_buf_sg_table_wrapper *copy; + + if (!IS_ENABLED(CONFIG_DMABUF_DEBUG)) + return; + + copy = container_of(*sg_table, typeof(*copy), wrapper); + *sg_table = copy->original; + sg_free_table(&copy->wrapper); + kfree(copy); } static inline bool @@ -1139,7 +1181,9 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach, if (ret < 0) goto error_unmap; } - mangle_sg_table(sg_table); + ret = dma_buf_mangle_sg_table(&sg_table); + if (ret) + goto error_unmap; if (IS_ENABLED(CONFIG_DMA_API_DEBUG)) { struct scatterlist *sg; @@ -1220,7 +1264,7 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach, dma_resv_assert_held(attach->dmabuf->resv); - mangle_sg_table(sg_table); + dma_buf_demangle_sg_table(&sg_table); attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction); if (dma_buf_pin_on_map(attach)) -- 2.43.0

7 months, 2 weeks

[RFC v2 06/11] nvme-pci: add support for dmabuf reggistration

by asml.silence＠gmail.com

The content of this message was lost. It was probably cross-posted to multiple lists and previously handled on another list.

7 months, 2 weeks

[RFC v2 07/11] nvme-pci: implement dma_token backed requests

by asml.silence＠gmail.com

The content of this message was lost. It was probably cross-posted to multiple lists and previously handled on another list.

7 months, 2 weeks

[PATCH v6 3/8] rust: drm: gem: Add raw_dma_resv() function

by Lyude Paul

For retrieving a pointer to the struct dma_resv for a given GEM object. We also introduce it in a new trait, BaseObjectPrivate, which we automatically implement for all gem objects and don't expose to users outside of the crate. Signed-off-by: Lyude Paul <lyude(a)redhat.com> --- rust/kernel/drm/gem/mod.rs | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs index 5c215e83c1b09..ec3c1b1775196 100644 --- a/rust/kernel/drm/gem/mod.rs +++ b/rust/kernel/drm/gem/mod.rs @@ -199,6 +199,18 @@ fn create_mmap_offset(&self) -> Result<u64> { impl<T: IntoGEMObject> BaseObject for T {} +/// Crate-private base operations shared by all GEM object classes. +#[expect(unused)] +pub(crate) trait BaseObjectPrivate: IntoGEMObject { + /// Return a pointer to this object's dma_resv. + fn raw_dma_resv(&self) -> *mut bindings::dma_resv { + // SAFETY: `as_gem_obj()` always returns a valid pointer to the base DRM gem object + unsafe { (*self.as_raw()).resv } + } +} + +impl<T: IntoGEMObject> BaseObjectPrivate for T {} + /// A base GEM object. /// /// # Invariants -- 2.52.0

7 months, 3 weeks

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