From e873c74132f0c5f1452816cd9bb26208f0bba1e1 Mon Sep 17 00:00:00 2001 From: Shivank Garg Date: Sat, 22 Aug 2026 19:22:05 +0000 Subject: dmaengine: fix use-after-free in dma_chan_put() and dma_release_channel() When dma_device_put() drops the last reference on chan->device->ref, dma_device_release() runs and may free the dma_device along with its channels. dma_chan_put() then still reads chan->device->owner via dma_chan_to_owner() for the trailing module_put(). KASAN catches it: slab-use-after-free in dma_chan_put+0x3e6/0x4c0 Read of size 8 by task insmod/6319 Freed by task 6319: kfree+0x225/0x470 dma_chan_put+0x395/0x4c0 dmaengine_put+0xf8/0x160 Cache the module owner in dma_chan_put() before the put so the trailing module_put() does not need chan->device. Fixes: 8ad342a86359 ("dmaengine: Add reference counting to dma_device struct") Suggested-by: Sashiko Link: https://sashiko.dev/#/patchset/20260518-dmaengine-kref-fix-v1-1-4d6125048fb7@amd.com Reviewed-by: Frank Li Reviewed-by: Logan Gunthorpe Signed-off-by: Shivank Garg Link: https://patch.msgid.link/20260822-dmaengine-kref-fix-v5-3-d4a4ee47d927@amd.com Signed-off-by: Vinod Koul --- Documentation/admin-guide/sysctl/user.rst | 84 +++++++++++++++++++++++++++++++ 1 file changed, 84 insertions(+) create mode 100644 Documentation/admin-guide/sysctl/user.rst (limited to 'Documentation/admin-guide/sysctl/user.rst') diff --git a/Documentation/admin-guide/sysctl/user.rst b/Documentation/admin-guide/sysctl/user.rst new file mode 100644 index 000000000..c45824589 --- /dev/null +++ b/Documentation/admin-guide/sysctl/user.rst @@ -0,0 +1,84 @@ +================================= +Documentation for /proc/sys/user/ +================================= + +kernel version 4.9.0 + +Copyright (c) 2016 Eric Biederman + +------------------------------------------------------------------------------ + +This file contains the documentation for the sysctl files in +/proc/sys/user. + +The files in this directory can be used to override the default +limits on the number of namespaces and other objects that have +per user per user namespace limits. + +The primary purpose of these limits is to stop programs that +malfunction and attempt to create a ridiculous number of objects, +before the malfunction becomes a system wide problem. It is the +intention that the defaults of these limits are set high enough that +no program in normal operation should run into these limits. + +The creation of per user per user namespace objects are charged to +the user in the user namespace who created the object and +verified to be below the per user limit in that user namespace. + +The creation of objects is also charged to all of the users +who created user namespaces the creation of the object happens +in (user namespaces can be nested) and verified to be below the per user +limits in the user namespaces of those users. + +This recursive counting of created objects ensures that creating a +user namespace does not allow a user to escape their current limits. + +Currently, these files are in /proc/sys/user: + +max_cgroup_namespaces +===================== + + The maximum number of cgroup namespaces that any user in the current + user namespace may create. + +max_ipc_namespaces +================== + + The maximum number of ipc namespaces that any user in the current + user namespace may create. + +max_mnt_namespaces +================== + + The maximum number of mount namespaces that any user in the current + user namespace may create. + +max_net_namespaces +================== + + The maximum number of network namespaces that any user in the + current user namespace may create. + +max_pid_namespaces +================== + + The maximum number of pid namespaces that any user in the current + user namespace may create. + +max_time_namespaces +=================== + + The maximum number of time namespaces that any user in the current + user namespace may create. + +max_user_namespaces +=================== + + The maximum number of user namespaces that any user in the current + user namespace may create. + +max_uts_namespaces +================== + + The maximum number of user namespaces that any user in the current + user namespace may create. -- cgit v1.3.1