kernel/git/stable/linux.git/fs/squashfs, branch master

squashfs: avoid thundering-herd cache wakeups

2026-08-20T02:55:06+00:00

squashfs_cache_get() puts a task to sleep when its block is not cached and every cache entry is busy. Those sleeps are non-exclusive, so the nr_exclusive == 1 budget squashfs_cache_put() has always passed to wake_up() is inert and one release makes every waiter runnable. A wakee only returns to squashfs_cache_get() if it observes cache->unused before the entry is reclaimed; later wakees see zero and re-queue inside wait_event() without rescanning. One freed entry satisfies exactly one capacity waiter, so waking the rest is waste. On a Meta production host serving a Python web application from a packaged squashfs image, a 30-second trace caught 1,045,132 cache-release wake calls and 19,511,556 wakeups: 18.7 per release, although each release added only one reusable cache entry. This was causing significant spikes in CPU usage. Make the waits exclusive, enqueueing while still holding cache->lock so that a concurrent lookup either sees the waiter queued or the waiter sees the block that lookup publishes. Two things follow. A wakee cannot be assumed to consume the entry it was woken for: it may find its own block published meanwhile, share that entry, and leave the freed one unclaimed. So a wakee which shares hands its wakeup on to the next waiter, as commit 0ddad21d3e99 ("pipe: use exclusive waits when reading or writing") does with wake_next_reader. And a waiter can now sleep through a publication of the very block it wants, which the old broadcast gave it repeated chances to notice. So waiters are keyed by block: publishing wakes every waiter for that block (nr_exclusive == 0), freeing an entry wakes one. That needs a custom wake callback, like wake_page_function() in mm/filemap.c, which also records which wakeup arrived so the handoff only fires for a capacity wakee. Broadcast is kept where more than one task can proceed - every waiter for a published block, and the wake_up_all() on entry->wait_queue - at the cost of walking the queue under wait_queue.lock to test the key. Waiters are now served FIFO with a scheduling round trip per handoff hop, so per-waiter latency changes; the filebench run below is 4x oversubscribed, where that should hurt most. Measured on a 32-CPU VM against a read-only squashfs (gzip, DECOMP_MULTI_PERCPU, FILE_DIRECT, default 8 metadata / 3 fragment cache entries) staged in tmpfs, page cache dropped each iteration to force cold decompression: elbencho, 64 threads metadata stat 700 -> 1320 files/s 1.9x small-file read 40 -> 60 MiB/s 1.5x filebench, 128 threads, open+read+stat+close (mean of 3x 30s) throughput 11,314 -> 25,186 ops/s 2.2x sched:sched_wakeup 27.0 -> 4.55 per op 5.9x fewer context switches 37.2 -> 7.64 per op 4.9x fewer Wakeups and context switches are per operation, since the two runs did 2.2x different amounts of work. Workloads which never queue for a cache entry gain no wakeups. Link: https://lore.kernel.org/20260807172421.3875982-1-usama.arif@linux.dev Signed-off-by: Usama Arif Reviewed-by: Phillip Lougher Cc: Boris Burkov Cc: Christian Brauner Cc: Jeff Layton Cc: Johannes Weiner Cc: Rik van Riel Cc: Shakeel Butt Signed-off-by: Andrew Morton

Squashfs: check block offset is not negative

2026-08-13T22:42:08+00:00

If a negative offset is read off disk (for example the offset into the decompressed fragment block), this will cause squashfs_copy_data() to perform an out of bounds access. Fix by checking if offset is negative, and returning 0. This matches existing behaviour where an offset beyond the block returns 0 bytes copied. To trigger this out of bounds access requires a crafted Squashfs filesystem and CAP_SYS_ADMIN to mount it. Unprivileged users will not be able to mount such a filesystem, but once mounted, an unprivileged user can trigger the out of bounds access by reading the crafted file with the negative offset. Link: https://lore.kernel.org/20260807162951.672510-1-phillip@squashfs.org.uk Fixes: f400e12656ab ("Squashfs: cache operations") Signed-off-by: Phillip Lougher Reported-by: Yuejie Shi Closes: https://lore.kernel.org/all/20260803032735.81785-1-syjcnss@gmail.com/ Signed-off-by: Andrew Morton

Squashfs: check metadata block offset is within range

2026-02-24T19:13:27+00:00

Syzkaller reports a "general protection fault in squashfs_copy_data" This is ultimately caused by a corrupted index look-up table, which produces a negative metadata block offset. This is subsequently passed to squashfs_copy_data (via squashfs_read_metadata) where the negative offset causes an out of bounds access. The fix is to check that the offset is within range in squashfs_read_metadata. This will trap this and other cases. Link: https://lkml.kernel.org/r/20260217050955.138351-1-phillip@squashfs.org.uk Fixes: f400e12656ab ("Squashfs: cache operations") Reported-by: syzbot+a9747fe1c35a5b115d3f@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/699234e2.a70a0220.2c38d7.00e2.GAE@google.com/ Signed-off-by: Phillip Lougher Cc: Christian Brauner Cc: Signed-off-by: Andrew Morton

Convert remaining multi-line kmalloc_obj/flex GFP_KERNEL uses

2026-02-22T16:26:33+00:00

Conversion performed via this Coccinelle script: // SPDX-License-Identifier: GPL-2.0-only // Options: --include-headers-for-types --all-includes --include-headers --keep-comments virtual patch @gfp depends on patch && !(file in "tools") && !(file in "samples")@ identifier ALLOC = {kmalloc_obj,kmalloc_objs,kmalloc_flex, kzalloc_obj,kzalloc_objs,kzalloc_flex, kvmalloc_obj,kvmalloc_objs,kvmalloc_flex, kvzalloc_obj,kvzalloc_objs,kvzalloc_flex}; @@ ALLOC(... - , GFP_KERNEL ) $ make coccicheck MODE=patch COCCI=gfp.cocci Build and boot tested x86_64 with Fedora 42's GCC and Clang: Linux version 6.19.0+ (user@host) (gcc (GCC) 15.2.1 20260123 (Red Hat 15.2.1-7), GNU ld version 2.44-12.fc42) #1 SMP PREEMPT_DYNAMIC 1970-01-01 Linux version 6.19.0+ (user@host) (clang version 20.1.8 (Fedora 20.1.8-4.fc42), LLD 20.1.8) #1 SMP PREEMPT_DYNAMIC 1970-01-01 Signed-off-by: Kees Cook Signed-off-by: Linus Torvalds

Convert 'alloc_obj' family to use the new default GFP_KERNEL argument

2026-02-22T01:09:51+00:00

This was done entirely with mindless brute force, using git grep -l '\

treewide: Replace kmalloc with kmalloc_obj for non-scalar types

2026-02-21T09:02:28+00:00

This is the result of running the Coccinelle script from scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to avoid scalar types (which need careful case-by-case checking), and instead replace kmalloc-family calls that allocate struct or union object instances: Single allocations: kmalloc(sizeof(TYPE), ...) are replaced with: kmalloc_obj(TYPE, ...) Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...) are replaced with: kmalloc_objs(TYPE, COUNT, ...) Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...) are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...) (where TYPE may also be *VAR) The resulting allocations no longer return "void *", instead returning "TYPE *". Signed-off-by: Kees Cook

squashfs: add setlease file operation

2026-01-12T09:55:47+00:00

Add the setlease file_operation pointing to generic_setlease to the squashfs file_operations structures. A future patch will change the default behavior to reject lease attempts with -EINVAL when there is no setlease file operation defined. Add generic_setlease to retain the ability to set leases on this filesystem. Signed-off-by: Jeff Layton Link: https://patch.msgid.link/20260108-setlease-6-20-v1-18-ea4dec9b67fa@kernel.org Acked-by: Al Viro Acked-by: Christoph Hellwig Signed-off-by: Christian Brauner

Coccinelle-based conversion to use ->i_state accessors

2025-10-20T18:22:26+00:00

All places were patched by coccinelle with the default expecting that ->i_lock is held, afterwards entries got fixed up by hand to use unlocked variants as needed. The script: @@ expression inode, flags; @@ - inode->i_state & flags + inode_state_read(inode) & flags @@ expression inode, flags; @@ - inode->i_state &= ~flags + inode_state_clear(inode, flags) @@ expression inode, flag1, flag2; @@ - inode->i_state &= ~flag1 & ~flag2 + inode_state_clear(inode, flag1 | flag2) @@ expression inode, flags; @@ - inode->i_state |= flags + inode_state_set(inode, flags) @@ expression inode, flags; @@ - inode->i_state = flags + inode_state_assign(inode, flags) @@ expression inode, flags; @@ - flags = inode->i_state + flags = inode_state_read(inode) @@ expression inode, flags; @@ - READ_ONCE(inode->i_state) & flags + inode_state_read(inode) & flags Signed-off-by: Mateusz Guzik Signed-off-by: Christian Brauner

Merge tag 'mm-nonmm-stable-2025-10-02-15-29' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2025-10-03T01:44:54+00:00

Pull non-MM updates from Andrew Morton: - "ida: Remove the ida_simple_xxx() API" from Christophe Jaillet completes the removal of this legacy IDR API - "panic: introduce panic status function family" from Jinchao Wang provides a number of cleanups to the panic code and its various helpers, which were rather ad-hoc and scattered all over the place - "tools/delaytop: implement real-time keyboard interaction support" from Fan Yu adds a few nice user-facing usability changes to the delaytop monitoring tool - "efi: Fix EFI boot with kexec handover (KHO)" from Evangelos Petrongonas fixes a panic which was happening with the combination of EFI and KHO - "Squashfs: performance improvement and a sanity check" from Phillip Lougher teaches squashfs's lseek() about SEEK_DATA/SEEK_HOLE. A mere 150x speedup was measured for a well-chosen microbenchmark - plus another 50-odd singleton patches all over the place * tag 'mm-nonmm-stable-2025-10-02-15-29' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (75 commits) Squashfs: reject negative file sizes in squashfs_read_inode() kallsyms: use kmalloc_array() instead of kmalloc() MAINTAINERS: update Sibi Sankar's email address Squashfs: add SEEK_DATA/SEEK_HOLE support Squashfs: add additional inode sanity checking lib/genalloc: fix device leak in of_gen_pool_get() panic: remove CONFIG_PANIC_ON_OOPS_VALUE ocfs2: fix double free in user_cluster_connect() checkpatch: suppress strscpy warnings for userspace tools cramfs: fix incorrect physical page address calculation kernel: prevent prctl(PR_SET_PDEATHSIG) from racing with parent process exit Squashfs: fix uninit-value in squashfs_get_parent kho: only fill kimage if KHO is finalized ocfs2: avoid extra calls to strlen() after ocfs2_sprintf_system_inode_name() kernel/sys.c: fix the racy usage of task_lock(tsk->group_leader) in sys_prlimit64() paths sched/task.h: fix the wrong comment on task_lock() nesting with tasklist_lock coccinelle: platform_no_drv_owner: handle also built-in drivers coccinelle: of_table: handle SPI device ID tables lib/decompress: use designated initializers for struct compress_format efi: support booting with kexec handover (KHO) ...

Squashfs: reject negative file sizes in squashfs_read_inode()

2025-09-28T18:36:15+00:00

Syskaller reports a "WARNING in ovl_copy_up_file" in overlayfs. This warning is ultimately caused because the underlying Squashfs file system returns a file with a negative file size. This commit checks for a negative file size and returns EINVAL. [phillip@squashfs.org.uk: only need to check 64 bit quantity] Link: https://lkml.kernel.org/r/20250926222305.110103-1-phillip@squashfs.org.uk Link: https://lkml.kernel.org/r/20250926215935.107233-1-phillip@squashfs.org.uk Fixes: 6545b246a2c8 ("Squashfs: inode operations") Signed-off-by: Phillip Lougher Reported-by: syzbot+f754e01116421e9754b9@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/68d580e5.a00a0220.303701.0019.GAE@google.com/ Cc: Amir Goldstein Cc: Signed-off-by: Andrew Morton