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/ABI/testing/evm | 109 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 109 insertions(+) create mode 100644 Documentation/ABI/testing/evm (limited to 'Documentation/ABI/testing/evm') diff --git a/Documentation/ABI/testing/evm b/Documentation/ABI/testing/evm new file mode 100644 index 000000000..db3007bab --- /dev/null +++ b/Documentation/ABI/testing/evm @@ -0,0 +1,109 @@ +What: /sys/kernel/security/evm +What: /sys/kernel/security/*/evm +Date: March 2011 +Contact: Mimi Zohar +Description: + EVM protects a file's security extended attributes(xattrs) + against integrity attacks. The initial method maintains an + HMAC-sha1 value across the extended attributes, storing the + value as the extended attribute 'security.evm'. + + EVM supports two classes of security.evm. The first is + an HMAC-sha1 generated locally with a + trusted/encrypted key stored in the Kernel Key + Retention System. The second is a digital signature + generated either locally or remotely using an + asymmetric key. These keys are loaded onto root's + keyring using keyctl, and EVM is then enabled by + echoing a value to /evm made up of the + following bits: + + === ================================================== + Bit Effect + === ================================================== + 0 Enable HMAC validation and creation + 1 Enable digital signature validation + 2 Permit modification of EVM-protected metadata at + runtime. Not supported if HMAC validation and + creation is enabled (deprecated). + 3 Require asymmetric signatures to be version 3 + 31 Disable further runtime modification of EVM policy + === ================================================== + + For example:: + + echo 1 >/evm + + will enable HMAC validation and creation + + :: + + echo 0x80000003 >/evm + + will enable HMAC and digital signature validation and + HMAC creation and disable all further modification of policy. + + :: + + echo 0x80000006 >/evm + + will enable digital signature validation, permit + modification of EVM-protected metadata and + disable all further modification of policy. This option is now + deprecated in favor of:: + + echo 0x80000002 >/evm + + as the outstanding issues that prevent the usage of EVM portable + signatures have been solved. + + Echoing a value is additive, the new value is added to the + existing initialization flags. + + For example, after:: + + echo 2 >/evm + + another echo can be performed:: + + echo 1 >/evm + + and the resulting value will be 3. + + Note that once an HMAC key has been loaded, it will no longer + be possible to enable metadata modification. Signaling that an + HMAC key has been loaded will clear the corresponding flag. + For example, if the current value is 6 (2 and 4 set):: + + echo 1 >/evm + + will set the new value to 3 (4 cleared). + + Loading an HMAC key is the only way to disable metadata + modification. + + Until key loading has been signaled EVM can not create + or validate the 'security.evm' xattr, but returns + INTEGRITY_UNKNOWN. Loading keys and signaling EVM + should be done as early as possible. Normally this is + done in the initramfs, which has already been measured + as part of the trusted boot. For more information on + creating and loading existing trusted/encrypted keys, + refer to: + Documentation/security/keys/trusted-encrypted.rst. Both + dracut (via 97masterkey and 98integrity) and systemd (via + core/ima-setup) have support for loading keys at boot + time. + +What: /sys/kernel/security/*/evm/evm_xattrs +Date: April 2018 +Contact: Matthew Garrett +Description: + Shows the set of extended attributes used to calculate or + validate the EVM signature, and allows additional attributes + to be added at runtime. Any signatures generated after + additional attributes are added (and on files possessing those + additional attributes) will only be valid if the same + additional attributes are configured on system boot. Writing + a single period (.) will lock the xattr list from any further + modification. -- cgit v1.3.1