From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions When using eBPF to probe CS CALL instructions within a function, a crash can be triggered. The eBPF tool probes offset 257 of the __hrtimer_run_queues() function: <__hrtimer_run_queues+249>: nopl 0x0(%rax,%rax,1) <__hrtimer_run_queues+254>: mov %r14,%rdi <__hrtimer_run_queues+257>: cs call <__x86_indirect_thunk_r12> <__hrtimer_run_queues+263>: mov %eax,%r12d <__hrtimer_run_queues+266>: xchg %ax,%ax <__hrtimer_run_queues+268>: mov %r13,%rdi Which triggers this crash: BUG: unable to handle page fault for address: 00000000000f41c9 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] SMP NOPTI CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P RIP: 0010:__hrtimer_run_queues+0x106/0x230 Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is at the 6th byte of the above CS CALL instruction. Since the CS CALL instruction occupies 6 bytes, the exception occurred in the middle of that call instruction. The root cause is that when using eBPF tools to probe in the middle of a function, a kprobe with INT3 is used as the underlying implementation. During single-step emulation of the original CALL instruction, int3_emulate_call() assumes that the probed CALL instruction is 5 bytes long. However, the actual CS-prefixed CALL instruction occupies 6 bytes, so it constructs an incorrect exception return address. When the CPU returns from the kprobe handler, the next instruction to be executed is at the address of the last byte of that CS CALL instruction. Coincidentally, starting from that address, the CPU fetches and decodes a completely different instruction, which ultimately triggers a kernel crash. Fix the issue by using the actual instruction length obtained from the instruction decoder when constructing the exception return address, rather than relying on the hardcoded CALL_INSN_SIZE macro. [ mingo: Refined the changelog ] Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step") Suggested-by: Masami Hiramatsu (Google) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- fs/jffs2/super.c | 443 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 443 insertions(+) create mode 100644 fs/jffs2/super.c (limited to 'fs/jffs2/super.c') diff --git a/fs/jffs2/super.c b/fs/jffs2/super.c new file mode 100644 index 000000000..81396a092 --- /dev/null +++ b/fs/jffs2/super.c @@ -0,0 +1,443 @@ +/* + * JFFS2 -- Journalling Flash File System, Version 2. + * + * Copyright © 2001-2007 Red Hat, Inc. + * + * Created by David Woodhouse + * + * For licensing information, see the file 'LICENCE' in this directory. + * + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include "compr.h" +#include "nodelist.h" + +static void jffs2_put_super(struct super_block *); + +static struct kmem_cache *jffs2_inode_cachep; + +static struct inode *jffs2_alloc_inode(struct super_block *sb) +{ + struct jffs2_inode_info *f; + + f = alloc_inode_sb(sb, jffs2_inode_cachep, GFP_KERNEL); + if (!f) + return NULL; + return &f->vfs_inode; +} + +static void jffs2_free_inode(struct inode *inode) +{ + struct jffs2_inode_info *f = JFFS2_INODE_INFO(inode); + + kfree(f->target); + kmem_cache_free(jffs2_inode_cachep, f); +} + +static void jffs2_i_init_once(void *foo) +{ + struct jffs2_inode_info *f = foo; + + mutex_init(&f->sem); + f->target = NULL; + inode_init_once(&f->vfs_inode); +} + +static const char *jffs2_compr_name(unsigned int compr) +{ + switch (compr) { + case JFFS2_COMPR_MODE_NONE: + return "none"; +#ifdef CONFIG_JFFS2_LZO + case JFFS2_COMPR_MODE_FORCELZO: + return "lzo"; +#endif +#ifdef CONFIG_JFFS2_ZLIB + case JFFS2_COMPR_MODE_FORCEZLIB: + return "zlib"; +#endif + default: + /* should never happen; programmer error */ + WARN_ON(1); + return ""; + } +} + +static int jffs2_show_options(struct seq_file *s, struct dentry *root) +{ + struct jffs2_sb_info *c = JFFS2_SB_INFO(root->d_sb); + struct jffs2_mount_opts *opts = &c->mount_opts; + + if (opts->override_compr) + seq_printf(s, ",compr=%s", jffs2_compr_name(opts->compr)); + if (opts->set_rp_size) + seq_printf(s, ",rp_size=%u", opts->rp_size / 1024); + + return 0; +} + +static int jffs2_sync_fs(struct super_block *sb, int wait) +{ + struct jffs2_sb_info *c = JFFS2_SB_INFO(sb); + +#ifdef CONFIG_JFFS2_FS_WRITEBUFFER + if (jffs2_is_writebuffered(c)) + cancel_delayed_work_sync(&c->wbuf_dwork); +#endif + + mutex_lock(&c->alloc_sem); + jffs2_flush_wbuf_pad(c); + mutex_unlock(&c->alloc_sem); + return 0; +} + +static struct inode *jffs2_nfs_get_inode(struct super_block *sb, uint64_t ino, + uint32_t generation) +{ + /* We don't care about i_generation. We'll destroy the flash + before we start re-using inode numbers anyway. And even + if that wasn't true, we'd have other problems...*/ + return jffs2_iget(sb, ino); +} + +static struct dentry *jffs2_fh_to_dentry(struct super_block *sb, struct fid *fid, + int fh_len, int fh_type) +{ + return generic_fh_to_dentry(sb, fid, fh_len, fh_type, + jffs2_nfs_get_inode); +} + +static struct dentry *jffs2_fh_to_parent(struct super_block *sb, struct fid *fid, + int fh_len, int fh_type) +{ + return generic_fh_to_parent(sb, fid, fh_len, fh_type, + jffs2_nfs_get_inode); +} + +static struct dentry *jffs2_get_parent(struct dentry *child) +{ + struct jffs2_inode_info *f; + uint32_t pino; + + BUG_ON(!d_is_dir(child)); + + f = JFFS2_INODE_INFO(d_inode(child)); + + pino = f->inocache->pino_nlink; + + JFFS2_DEBUG("Parent of directory ino #%u is #%u\n", + f->inocache->ino, pino); + + return d_obtain_alias(jffs2_iget(child->d_sb, pino)); +} + +static const struct export_operations jffs2_export_ops = { + .encode_fh = generic_encode_ino32_fh, + .get_parent = jffs2_get_parent, + .fh_to_dentry = jffs2_fh_to_dentry, + .fh_to_parent = jffs2_fh_to_parent, +}; + +/* + * JFFS2 mount options. + * + * Opt_source: The source device + * Opt_override_compr: override default compressor + * Opt_rp_size: size of reserved pool in KiB + */ +enum { + Opt_override_compr, + Opt_rp_size, +}; + +static const struct constant_table jffs2_param_compr[] = { + {"none", JFFS2_COMPR_MODE_NONE }, +#ifdef CONFIG_JFFS2_LZO + {"lzo", JFFS2_COMPR_MODE_FORCELZO }, +#endif +#ifdef CONFIG_JFFS2_ZLIB + {"zlib", JFFS2_COMPR_MODE_FORCEZLIB }, +#endif + {} +}; + +static const struct fs_parameter_spec jffs2_fs_parameters[] = { + fsparam_enum ("compr", Opt_override_compr, jffs2_param_compr), + fsparam_u32 ("rp_size", Opt_rp_size), + {} +}; + +static int jffs2_parse_param(struct fs_context *fc, struct fs_parameter *param) +{ + struct fs_parse_result result; + struct jffs2_sb_info *c = fc->s_fs_info; + int opt; + + opt = fs_parse(fc, jffs2_fs_parameters, param, &result); + if (opt < 0) + return opt; + + switch (opt) { + case Opt_override_compr: + c->mount_opts.compr = result.uint_32; + c->mount_opts.override_compr = true; + break; + case Opt_rp_size: + if (result.uint_32 > UINT_MAX / 1024) + return invalf(fc, "jffs2: rp_size unrepresentable"); + c->mount_opts.rp_size = result.uint_32 * 1024; + c->mount_opts.set_rp_size = true; + break; + default: + return -EINVAL; + } + + return 0; +} + +static inline void jffs2_update_mount_opts(struct fs_context *fc) +{ + struct jffs2_sb_info *new_c = fc->s_fs_info; + struct jffs2_sb_info *c = JFFS2_SB_INFO(fc->root->d_sb); + + mutex_lock(&c->alloc_sem); + if (new_c->mount_opts.override_compr) { + c->mount_opts.override_compr = new_c->mount_opts.override_compr; + c->mount_opts.compr = new_c->mount_opts.compr; + } + if (new_c->mount_opts.set_rp_size) { + c->mount_opts.set_rp_size = new_c->mount_opts.set_rp_size; + c->mount_opts.rp_size = new_c->mount_opts.rp_size; + } + mutex_unlock(&c->alloc_sem); +} + +static int jffs2_reconfigure(struct fs_context *fc) +{ + struct super_block *sb = fc->root->d_sb; + + sync_filesystem(sb); + jffs2_update_mount_opts(fc); + + return jffs2_do_remount_fs(sb, fc); +} + +static const struct super_operations jffs2_super_operations = +{ + .alloc_inode = jffs2_alloc_inode, + .free_inode = jffs2_free_inode, + .put_super = jffs2_put_super, + .statfs = jffs2_statfs, + .evict_inode = jffs2_evict_inode, + .dirty_inode = jffs2_dirty_inode, + .show_options = jffs2_show_options, + .sync_fs = jffs2_sync_fs, +}; + +/* + * fill in the superblock + */ +static int jffs2_fill_super(struct super_block *sb, struct fs_context *fc) +{ + struct jffs2_sb_info *c = sb->s_fs_info; + + jffs2_dbg(1, "jffs2_get_sb_mtd():" + " New superblock for device %d (\"%s\")\n", + sb->s_mtd->index, sb->s_mtd->name); + + c->mtd = sb->s_mtd; + c->os_priv = sb; + + if (c->mount_opts.rp_size > c->mtd->size) + return invalf(fc, "jffs2: Too large reserve pool specified, max is %llu KB", + c->mtd->size / 1024); + + /* Initialize JFFS2 superblock locks, the further initialization will + * be done later */ + mutex_init(&c->alloc_sem); + mutex_init(&c->erase_free_sem); + init_waitqueue_head(&c->erase_wait); + init_waitqueue_head(&c->inocache_wq); + spin_lock_init(&c->erase_completion_lock); + spin_lock_init(&c->inocache_lock); + + sb->s_op = &jffs2_super_operations; + sb->s_export_op = &jffs2_export_ops; + sb->s_flags = sb->s_flags | SB_NOATIME; + sb->s_xattr = jffs2_xattr_handlers; +#ifdef CONFIG_JFFS2_FS_POSIX_ACL + sb->s_flags |= SB_POSIXACL; +#endif + return jffs2_do_fill_super(sb, fc); +} + +static int jffs2_get_tree(struct fs_context *fc) +{ + return get_tree_mtd(fc, jffs2_fill_super); +} + +static void jffs2_free_fc(struct fs_context *fc) +{ + kfree(fc->s_fs_info); +} + +static const struct fs_context_operations jffs2_context_ops = { + .free = jffs2_free_fc, + .parse_param = jffs2_parse_param, + .get_tree = jffs2_get_tree, + .reconfigure = jffs2_reconfigure, +}; + +static int jffs2_init_fs_context(struct fs_context *fc) +{ + struct jffs2_sb_info *ctx; + + ctx = kzalloc_obj(struct jffs2_sb_info); + if (!ctx) + return -ENOMEM; + + fc->s_fs_info = ctx; + fc->ops = &jffs2_context_ops; + return 0; +} + +static void jffs2_put_super (struct super_block *sb) +{ + struct jffs2_sb_info *c = JFFS2_SB_INFO(sb); + + jffs2_dbg(2, "%s()\n", __func__); + + mutex_lock(&c->alloc_sem); + jffs2_flush_wbuf_pad(c); + mutex_unlock(&c->alloc_sem); + + jffs2_sum_exit(c); + + jffs2_free_ino_caches(c); + jffs2_free_raw_node_refs(c); + kvfree(c->blocks); + jffs2_flash_cleanup(c); + kfree(c->inocache_list); + jffs2_clear_xattr_subsystem(c); + mtd_sync(c->mtd); + jffs2_dbg(1, "%s(): returning\n", __func__); +} + +static void jffs2_kill_sb(struct super_block *sb) +{ + struct jffs2_sb_info *c = JFFS2_SB_INFO(sb); + if (c && !sb_rdonly(sb)) + jffs2_stop_garbage_collect_thread(c); + kill_mtd_super(sb); + kfree(c); +} + +static struct file_system_type jffs2_fs_type = { + .owner = THIS_MODULE, + .name = "jffs2", + .init_fs_context = jffs2_init_fs_context, + .parameters = jffs2_fs_parameters, + .kill_sb = jffs2_kill_sb, +}; +MODULE_ALIAS_FS("jffs2"); + +static int __init init_jffs2_fs(void) +{ + int ret; + + /* Paranoia checks for on-medium structures. If we ask GCC + to pack them with __attribute__((packed)) then it _also_ + assumes that they're not aligned -- so it emits crappy + code on some architectures. Ideally we want an attribute + which means just 'no padding', without the alignment + thing. But GCC doesn't have that -- we have to just + hope the structs are the right sizes, instead. */ + BUILD_BUG_ON(sizeof(struct jffs2_unknown_node) != 12); + BUILD_BUG_ON(sizeof(struct jffs2_raw_dirent) != 40); + BUILD_BUG_ON(sizeof(struct jffs2_raw_inode) != 68); + BUILD_BUG_ON(sizeof(struct jffs2_raw_summary) != 32); + + pr_info("version 2.2." +#ifdef CONFIG_JFFS2_FS_WRITEBUFFER + " (NAND)" +#endif +#ifdef CONFIG_JFFS2_SUMMARY + " (SUMMARY) " +#endif + " © 2001-2006 Red Hat, Inc.\n"); + + jffs2_inode_cachep = kmem_cache_create("jffs2_i", + sizeof(struct jffs2_inode_info), + 0, (SLAB_RECLAIM_ACCOUNT| + SLAB_ACCOUNT), + jffs2_i_init_once); + if (!jffs2_inode_cachep) { + pr_err("error: Failed to initialise inode cache\n"); + return -ENOMEM; + } + ret = jffs2_compressors_init(); + if (ret) { + pr_err("error: Failed to initialise compressors\n"); + goto out; + } + ret = jffs2_create_slab_caches(); + if (ret) { + pr_err("error: Failed to initialise slab caches\n"); + goto out_compressors; + } + ret = register_filesystem(&jffs2_fs_type); + if (ret) { + pr_err("error: Failed to register filesystem\n"); + goto out_slab; + } + return 0; + + out_slab: + jffs2_destroy_slab_caches(); + out_compressors: + jffs2_compressors_exit(); + out: + kmem_cache_destroy(jffs2_inode_cachep); + return ret; +} + +static void __exit exit_jffs2_fs(void) +{ + unregister_filesystem(&jffs2_fs_type); + jffs2_destroy_slab_caches(); + jffs2_compressors_exit(); + + /* + * Make sure all delayed rcu free inodes are flushed before we + * destroy cache. + */ + rcu_barrier(); + kmem_cache_destroy(jffs2_inode_cachep); +} + +module_init(init_jffs2_fs); +module_exit(exit_jffs2_fs); + +MODULE_DESCRIPTION("The Journalling Flash File System, v2"); +MODULE_AUTHOR("Red Hat, Inc."); +MODULE_LICENSE("GPL"); // Actually dual-licensed, but it doesn't matter for + // the sake of this tag. It's Free Software. -- cgit v1.3.1