kernel/linux.git/fs/sysfs/file.c, branch v7.2-rc1

sysfs: clamp show() return value in sysfs_kf_read()

2026-05-20T15:15:20+00:00

sysfs_kf_seq_show() defends against buggy show() callbacks that return larger than PAGE_SIZE by clamping the value and printing a warning. sysfs_kf_read(), the prealloc variant, has no such defense. The only current in-tree user of __ATTR_PREALLOC is drivers/md/md.c, whose show() callbacks are well-behaved, so this is hardening against future drivers doing foolish things and out-of-tree code doing even more foolish things. Cc: NeilBrown Cc: Tejun Heo Fixes: 2b75869bba67 ("sysfs/kernfs: allow attributes to request write buffer be pre-allocated.") Assisted-by: gregkh_clanker_t1000 Reviewed-by: Rafael J. Wysocki (Intel) Reviewed-by: Danilo Krummrich Link: https://patch.msgid.link/2026052000-drove-unicycle-d61b@gregkh Signed-off-by: Greg Kroah-Hartman

sysfs: upgrade OOB write by buggy .show hook into WARNing

2026-05-07T10:31:51+00:00

Buggy .show hook will get just 1 line of dmesg: fill_read_buffer: ext4_attr_show+0x0/0x600 returned bad count It may or may not oops later in some unrelated process. But buggy .show hook most likely is corrupting random memory past sysfs buffer therefore deserving more. WARN, make it more visible and let QA machines panic earlier. Also, delete useless cast -- "count" is >=0 at this point. Signed-off-by: Alexey Dobriyan Reviewed-by: Danilo Krummrich Link: https://patch.msgid.link/3cc3e8c6-c6e8-4625-a88f-f5708b935dab@p183 Signed-off-by: Greg Kroah-Hartman

kernfs: pass struct ns_common instead of const void * for namespace tags

2026-04-09T12:36:52+00:00

kernfs has historically used const void * to pass around namespace tags used for directory-level namespace filtering. The only current user of this is sysfs network namespace tagging where struct net pointers are cast to void *. Replace all const void * namespace parameters with const struct ns_common * throughout the kernfs, sysfs, and kobject namespace layers. This includes the kobj_ns_type_operations callbacks, kobject_namespace(), and all sysfs/kernfs APIs that accept or return namespace tags. Passing struct ns_common is needed because various codepaths require access to the underlying namespace. A struct ns_common can always be converted back to the concrete namespace type (e.g., struct net) via container_of() or to_ns_common() in the reverse direction. This is a preparatory change for switching to ns_id-based directory iteration to prevent a KASLR pointer leak through the current use of raw namespace pointers as hash seeds and comparison keys. Signed-off-by: Christian Brauner

sysfs: remove exports of sysfs_*change_owner()

2026-02-05T15:49:38+00:00

Both sysfs_change_owner() and sysfs_file_change_owner() are exported to modules, but there are no in-kernel module users, so remove the exports so that crazy out-of-tree drivers don't get the impression that it is safe to call these functions at all. Reviewed-by: Rafael J. Wysocki (Intel) Reviewed-by: Danilo Krummrich Reported-by: Lee Jones Reviewed-by: Lee Jones Link: https://patch.msgid.link/2026020541-energize-graduate-981a@gregkh Signed-off-by: Greg Kroah-Hartman

sysfs: remove bin_attribute::read_new/write_new()

2025-08-19T11:12:12+00:00

These transitional fields are now unused and unnecessary. Remove them and their logic in the sysfs core. Signed-off-by: Thomas Weißschuh Link: https://lore.kernel.org/r/20250811-sysfs-const-bin_attr-final-v4-1-7b6053fd58bb@weissschuh.net Signed-off-by: Greg Kroah-Hartman

sysfs: constify internal references to 'struct bin_attribute'

2025-06-17T08:44:09+00:00

The sysfs core handles 'const struct bin_attribute *'. Adapt the internal references. Signed-off-by: Thomas Weißschuh Link: https://lore.kernel.org/r/20250530-sysfs-const-bin_attr-final-v3-2-724bfcf05b99@weissschuh.net Signed-off-by: Greg Kroah-Hartman

kernfs: Use RCU to access kernfs_node::parent.

2025-02-15T16:46:32+00:00

kernfs_rename_lock is used to obtain stable kernfs_node::{name|parent} pointer. This is a preparation to access kernfs_node::parent under RCU and ensure that the pointer remains stable under the RCU lifetime guarantees. For a complete path, as it is done in kernfs_path_from_node(), the kernfs_rename_lock is still required in order to obtain a stable parent relationship while computing the relevant node depth. This must not change while the nodes are inspected in order to build the path. If the kernfs user never moves the nodes (changes the parent) then the kernfs_rename_lock is not required and the RCU guarantees are sufficient. This "restriction" can be set with KERNFS_ROOT_INVARIANT_PARENT. Otherwise the lock is required. Rename kernfs_node::parent to kernfs_node::__parent to denote the RCU access and use RCU accessor while accessing the node. Make cgroup use KERNFS_ROOT_INVARIANT_PARENT since the parent here can not change. Acked-by: Tejun Heo Cc: Yonghong Song Signed-off-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/r/20250213145023.2820193-6-bigeasy@linutronix.de Signed-off-by: Greg Kroah-Hartman

sysfs: constify bin_attribute argument of sysfs_bin_attr_simple_read()

2025-01-09T09:43:58+00:00

Most users use this function through the BIN_ATTR_SIMPLE* macros, they can handle the switch transparently. Also adapt the two non-macro users in the same change. Signed-off-by: Thomas Weißschuh Acked-by: Madhavan Srinivasan Reviewed-by: Mahesh Salgaonkar Tested-by: Aditya Gupta Link: https://lore.kernel.org/r/20241228-sysfs-const-bin_attr-simple-v2-1-7c6f3f1767a3@weissschuh.net Signed-off-by: Greg Kroah-Hartman

sysfs: bin_attribute: add const read/write callback variants

2024-11-05T13:00:28+00:00

To make it possible to put struct bin_attribute into read-only memory, the sysfs core has to stop passing mutable pointers to the read() and write() callbacks. As there are numerous implementors of these callbacks throughout the tree it's not possible to change all of them at once. To enable a step-by-step transition, add new variants of the read() and write() callbacks which differ only in the constness of the struct bin_attribute argument. As most binary attributes are defined through macros, extend these macros to transparently handle both variants of callbacks to minimize the churn during the transition. As soon as all handlers are switch to the const variant, the non-const one can be removed together with the transition machinery. Signed-off-by: Thomas Weißschuh Acked-by: Krzysztof Wilczyński Link: https://lore.kernel.org/r/20241103-sysfs-const-bin_attr-v2-9-71110628844c@weissschuh.net Signed-off-by: Greg Kroah-Hartman

sysfs: explicitly pass size to sysfs_add_bin_file_mode_ns()

2024-11-05T13:00:28+00:00

Upcoming changes to the sysfs core require the size of the created file to be overridable by the caller. Add a parameter to enable this. For now keep using attr->size in all cases. Signed-off-by: Thomas Weißschuh Acked-by: Krzysztof Wilczyński Link: https://lore.kernel.org/r/20241103-sysfs-const-bin_attr-v2-1-71110628844c@weissschuh.net Signed-off-by: Greg Kroah-Hartman