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(unknown [36.110.52.2]) by APP-01 (Coremail) with SMTP id qwCowACnfvIrlaxqB_xECA--.11695S2; Fri, 18 Sep 2026 09:34:35 +0800 (CST) From: Jiakai Xu To: Gerd Hoffmann , Vivek Kasireddy , Sumit Semwal , =?UTF-8?q?Christian=20K=C3=B6nig?= , dri-devel@lists.freedesktop.org Cc: Huan Yang , Robert Mader , linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, Jiakai Xu Subject: [PATCH] dma-buf/udmabuf: avoid oversized kvmalloc in init_udmabuf() Date: Fri, 18 Sep 2026 01:34:34 +0000 Message-Id: <20260918013434.1849135-1-xujiakai24@mails.ucas.ac.cn> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: qwCowACnfvIrlaxqB_xECA--.11695S2 X-Coremail-Antispam: 1UD129KBjvJXoW3Gw1kKr48GFW7uryxCrWktFb_yoW7Xrykpr 4aqr4UCr40qF1DA3WUJFn8Jw1UAa1DAFW7W3y7Gr1kZF1UCw1UZFn7Gry8JryDGw1UZay7 tF1DAw40qr1UAaUanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUBq14x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26ryj6F1UM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26F4j 6r4UJwA2z4x0Y4vEx4A2jsIE14v26r4UJVWxJr1l84ACjcxK6I8E87Iv6xkF7I0E14v26r 4UJVWxJr1lnxkEFVAIw20F6cxK64vIFxWle2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG 64xvF2IEw4CE5I8CrVC2j2WlYx0E2Ix0cI8IcVAFwI0_JF0_Jw1lYx0Ex4A2jsIE14v26F 4j6r4UJwAm72CE4IkC6x0Yz7v_Jr0_Gr1lF7xvr2IYc2Ij64vIr41lF7I21c0EjII2zVCS 5cI20VAGYxC7M4IIrI8v6xkF7I0E8cxan2IY04v7MxkF7I0En4kS14v26r1q6r43MxAIw2 8IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMI8I3I0E5I8CrVAFwI0_Jr0_Jr4l x2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVWUtVW8ZwCIc40Y0x0EwIxGrw CI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8IcVCY1x0267AKxVW8JVWxJwCI 42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI0_Jr0_Gr1lIxAIcVC2z2 80aVCY1x0267AKxVW8JVW8JrUvcSsGvfC2KfnxnUUI43ZEXa7VU1-txDUUUUU== X-CM-SenderInfo: 50xmxthndljko6pdxz3voxutnvoduhdfq/ Content-Type: text/plain; charset="utf-8" init_udmabuf() allocates two pointer arrays with one entry per page of the created buffer. Since commit 1c0844c6184e ("udmabuf: change folios array from kmalloc to kvmalloc") these arrays are allocated with kvmalloc(), which warns and fails when the requested size exceeds INT_MAX bytes. With the default size limit of 64 MB the largest possible request was far below that threshold, but commit 44e9eb5a7621 ("dma-buf/udmabuf: Disable the size limit by default") raised the limit to INT_MAX MB. With 4K pages, creating a buffer of more than INT_MAX / 8 pages (about 1 TB of pinned memory) now makes kvmalloc() hit its "crazy size" WARN_ON_ONCE(), which is trivially triggerable from unprivileged users through the UDMABUF_CREATE ioctls: WARNING: CPU: 0 PID: 412 at mm/slub.c:7021 __kvmalloc_node_noprof Call Trace: udmabuf_create udmabuf_ioctl_create_list Fix it by rejecting buffers whose page count exceeds what the pointer arrays can address before calling init_udmabuf(), returning -EINVAL. Fixes: 1c0844c6184e ("udmabuf: change folios array from kmalloc to kvmalloc= ") Fixes: 44e9eb5a7621 ("dma-buf/udmabuf: Disable the size limit by default") Signed-off-by: Jiakai Xu --- drivers/dma-buf/udmabuf.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c index df6dd00462423..25984e75d7ff3 100644 --- a/drivers/dma-buf/udmabuf.c +++ b/drivers/dma-buf/udmabuf.c @@ -383,6 +383,14 @@ static long udmabuf_create(struct miscdevice *device, if (!pgcnt) goto err_noinit; =20 + /* + * init_udmabuf() allocates two arrays of pointers, one entry per + * page, with kvmalloc(), which cannot handle sizes larger than + * INT_MAX bytes. + */ + if (pgcnt > INT_MAX / sizeof(struct page *)) + goto err_noinit; + ret =3D init_udmabuf(ubuf, pgcnt); if (ret) goto err; --=20 2.34.1 --=20 Below is the crash report: ------------[ cut here ]------------ WARNING: mm/slub.c:7013 at __kvmalloc_node_noprof+0x516/0x5d0 home/zzzrrll/= tmp/kf_src/linux-7.3-rc2/mm/slub.c:7013, CPU#0: syz.5.27938/167363 Modules linked in: CPU: 0 UID: 0 PID: 167363 Comm: syz.5.27938 Tainted: G W L 7= .3.0-rc2 #1 PREEMPT(full)=20 Tainted: [W]=3DWARN, [L]=3DSOFTLOCKUP Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/= 2014 RIP: 0010:__kvmalloc_node_noprof+0x516/0x5d0 home/zzzrrll/tmp/kf_src/linux-= 7.3-rc2/mm/slub.c:7013 Code: 05 bf fa 2d 08 49 8b 0f c6 04 08 00 65 48 ff 0d 90 fa 2d 08 0f 85 4c = fd ff ff e8 05 43 8c ff e9 42 fd ff ff e8 9b 86 0e 04 90 <0f> 0b 90 31 db e= 9 d2 fe ff ff f3 0f 1e fa 65 8b 05 8d fa 2d 08 89 RSP: 0018:ffffc90002bc3cf8 EFLAGS: 00010246 RAX: 0000000000000100 RBX: 0000000000000000 RCX: 0000008000000000 RDX: 0000008000000000 RSI: 0000000000000000 RDI: ffffffff835e3226 RBP: 00000000ffffffff R08: 00000000000028c0 R09: 00000000ffffffff R10: 0000000000000006 R11: 0000000000000002 R12: 0000008000000000 R13: 00000000000028c0 R14: 0000001000000000 R15: 0000008000000000 FS: 00007fc89ae45640(0000) GS:ffff8880f3de4000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000110c2ff305 CR3: 000000002b3d4000 CR4: 0000000000752ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000006000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 PKRU: 80000000 Call Trace: init_udmabuf home/zzzrrll/tmp/kf_src/linux-7.3-rc2/drivers/dma-buf/udmabuf= .c:193 [inline] udmabuf_create+0x1b6/0x750 home/zzzrrll/tmp/kf_src/linux-7.3-rc2/drivers/d= ma-buf/udmabuf.c:386 udmabuf_ioctl_create home/zzzrrll/tmp/kf_src/linux-7.3-rc2/drivers/dma-buf= /udmabuf.c:465 [inline] udmabuf_ioctl+0x132/0x1d0 home/zzzrrll/tmp/kf_src/linux-7.3-rc2/drivers/dm= a-buf/udmabuf.c:496 vfs_ioctl home/zzzrrll/tmp/kf_src/linux-7.3-rc2/fs/ioctl.c:51 [inline] __do_sys_ioctl home/zzzrrll/tmp/kf_src/linux-7.3-rc2/fs/ioctl.c:597 [inlin= e] __se_sys_ioctl+0xbc/0x130 home/zzzrrll/tmp/kf_src/linux-7.3-rc2/fs/ioctl.c= :583 do_syscall_x64 home/zzzrrll/tmp/kf_src/linux-7.3-rc2/arch/x86/entry/syscal= l_64.c:61 [inline] do_syscall_64+0x12b/0x350 home/zzzrrll/tmp/kf_src/linux-7.3-rc2/arch/x86/e= ntry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x590d6d Code: 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa 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 f= f 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fc89ae44fd8 EFLAGS: 00000216 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000611e7f RCX: 0000000000590d6d RDX: 00002000000023c0 RSI: 0000000040187542 RDI: 000000000000000a RBP: 00007fc89ae45010 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000216 R12: 00007fc89ae45640 R13: 000000000000000b R14: 0000000000528d40 R15: 00007fc89ae25000 ---[ end trace 0000000000000000 ]--- ---