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/ext2/namei.c | 434 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 434 insertions(+) create mode 100644 fs/ext2/namei.c (limited to 'fs/ext2/namei.c') diff --git a/fs/ext2/namei.c b/fs/ext2/namei.c new file mode 100644 index 000000000..8666233ec --- /dev/null +++ b/fs/ext2/namei.c @@ -0,0 +1,434 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * linux/fs/ext2/namei.c + * + * Rewrite to pagecache. Almost all code had been changed, so blame me + * if the things go wrong. Please, send bug reports to + * viro@parcelfarce.linux.theplanet.co.uk + * + * Stuff here is basically a glue between the VFS and generic UNIXish + * filesystem that keeps everything in pagecache. All knowledge of the + * directory layout is in fs/ext2/dir.c - it turned out to be easily separatable + * and it's easier to debug that way. In principle we might want to + * generalize that a bit and turn it into a library. Or not. + * + * The only non-static object here is ext2_dir_inode_operations. + * + * Copyright (C) 1992, 1993, 1994, 1995 + * Remy Card (card@masi.ibp.fr) + * Laboratoire MASI - Institut Blaise Pascal + * Universite Pierre et Marie Curie (Paris VI) + * + * from + * + * linux/fs/minix/namei.c + * + * Copyright (C) 1991, 1992 Linus Torvalds + * + * Big-endian to little-endian byte-swapping/bitmaps by + * David S. Miller (davem@caip.rutgers.edu), 1995 + */ + +#include +#include +#include "ext2.h" +#include "xattr.h" +#include "acl.h" + +static inline int ext2_add_nondir(struct dentry *dentry, struct inode *inode) +{ + int err = ext2_add_link(dentry, inode); + if (!err) { + d_instantiate_new(dentry, inode); + return 0; + } + inode_dec_link_count(inode); + discard_new_inode(inode); + return err; +} + +/* + * Methods themselves. + */ + +static struct dentry *ext2_lookup(struct inode * dir, struct dentry *dentry, unsigned int flags) +{ + struct inode * inode; + ino_t ino; + int res; + + if (dentry->d_name.len > EXT2_NAME_LEN) + return ERR_PTR(-ENAMETOOLONG); + + res = ext2_inode_by_name(dir, &dentry->d_name, &ino); + if (res) { + if (res != -ENOENT) + return ERR_PTR(res); + inode = NULL; + } else { + inode = ext2_iget(dir->i_sb, ino); + if (inode == ERR_PTR(-ESTALE)) { + ext2_error(dir->i_sb, __func__, + "deleted inode referenced: %lu", + (unsigned long) ino); + return ERR_PTR(-EIO); + } + } + return d_splice_alias(inode, dentry); +} + +struct dentry *ext2_get_parent(struct dentry *child) +{ + ino_t ino; + int res; + + res = ext2_inode_by_name(d_inode(child), &dotdot_name, &ino); + if (res) + return ERR_PTR(res); + + return d_obtain_alias(ext2_iget(child->d_sb, ino)); +} + +/* + * By the time this is called, we already have created + * the directory cache entry for the new file, but it + * is so far negative - it has no inode. + * + * If the create succeeds, we fill in the inode information + * with d_instantiate(). + */ +static int ext2_create (struct mnt_idmap * idmap, + struct inode * dir, struct dentry * dentry, + umode_t mode) +{ + struct inode *inode; + int err; + + err = dquot_initialize(dir); + if (err) + return err; + + inode = ext2_new_inode(dir, mode, &dentry->d_name); + if (IS_ERR(inode)) + return PTR_ERR(inode); + + ext2_set_file_ops(inode); + mark_inode_dirty(inode); + return ext2_add_nondir(dentry, inode); +} + +static int ext2_tmpfile(struct mnt_idmap *idmap, struct inode *dir, + struct file *file, umode_t mode) +{ + struct inode *inode = ext2_new_inode(dir, mode, NULL); + if (IS_ERR(inode)) + return PTR_ERR(inode); + + ext2_set_file_ops(inode); + mark_inode_dirty(inode); + d_tmpfile(file, inode); + unlock_new_inode(inode); + return finish_open_simple(file, 0); +} + +static int ext2_mknod (struct mnt_idmap * idmap, struct inode * dir, + struct dentry *dentry, umode_t mode, dev_t rdev) +{ + struct inode * inode; + int err; + + err = dquot_initialize(dir); + if (err) + return err; + + inode = ext2_new_inode (dir, mode, &dentry->d_name); + err = PTR_ERR(inode); + if (!IS_ERR(inode)) { + init_special_inode(inode, inode->i_mode, rdev); + inode->i_op = &ext2_special_inode_operations; + mark_inode_dirty(inode); + err = ext2_add_nondir(dentry, inode); + } + return err; +} + +static int ext2_symlink (struct mnt_idmap * idmap, struct inode * dir, + struct dentry * dentry, const char * symname) +{ + struct super_block * sb = dir->i_sb; + int err = -ENAMETOOLONG; + unsigned l = strlen(symname)+1; + struct inode * inode; + + if (l > sb->s_blocksize) + goto out; + + err = dquot_initialize(dir); + if (err) + goto out; + + inode = ext2_new_inode (dir, S_IFLNK | S_IRWXUGO, &dentry->d_name); + err = PTR_ERR(inode); + if (IS_ERR(inode)) + goto out; + + if (l > sizeof (EXT2_I(inode)->i_data)) { + /* slow symlink */ + inode->i_op = &ext2_symlink_inode_operations; + inode_nohighmem(inode); + inode->i_mapping->a_ops = &ext2_aops; + err = page_symlink(inode, symname, l); + if (err) + goto out_fail; + } else { + /* fast symlink */ + inode->i_op = &ext2_fast_symlink_inode_operations; + inode->i_link = (char*)EXT2_I(inode)->i_data; + memcpy(inode->i_link, symname, l); + inode->i_size = l-1; + } + mark_inode_dirty(inode); + + err = ext2_add_nondir(dentry, inode); +out: + return err; + +out_fail: + inode_dec_link_count(inode); + discard_new_inode(inode); + goto out; +} + +static int ext2_link (struct dentry * old_dentry, struct inode * dir, + struct dentry *dentry) +{ + struct inode *inode = d_inode(old_dentry); + int err; + + err = dquot_initialize(dir); + if (err) + return err; + + inode_set_ctime_current(inode); + inode_inc_link_count(inode); + ihold(inode); + + err = ext2_add_link(dentry, inode); + if (!err) { + d_instantiate(dentry, inode); + return 0; + } + inode_dec_link_count(inode); + iput(inode); + return err; +} + +static struct dentry *ext2_mkdir(struct mnt_idmap * idmap, + struct inode * dir, struct dentry * dentry, + umode_t mode) +{ + struct inode * inode; + int err; + + err = dquot_initialize(dir); + if (err) + return ERR_PTR(err); + + inode_inc_link_count(dir); + + inode = ext2_new_inode(dir, mode, &dentry->d_name); + err = PTR_ERR(inode); + if (IS_ERR(inode)) + goto out_dir; + + inode->i_op = &ext2_dir_inode_operations; + inode->i_fop = &ext2_dir_operations; + inode->i_mapping->a_ops = &ext2_aops; + + inode_inc_link_count(inode); + + err = ext2_make_empty(inode, dir); + if (err) + goto out_fail; + + err = ext2_add_link(dentry, inode); + if (err) + goto out_fail; + + d_instantiate_new(dentry, inode); +out: + return ERR_PTR(err); + +out_fail: + inode_dec_link_count(inode); + inode_dec_link_count(inode); + discard_new_inode(inode); +out_dir: + inode_dec_link_count(dir); + goto out; +} + +static int ext2_unlink(struct inode *dir, struct dentry *dentry) +{ + struct inode *inode = d_inode(dentry); + struct ext2_dir_entry_2 *de; + struct folio *folio; + int err; + + err = dquot_initialize(dir); + if (err) + goto out; + + de = ext2_find_entry(dir, &dentry->d_name, &folio); + if (IS_ERR(de)) { + err = PTR_ERR(de); + goto out; + } + + err = ext2_delete_entry(de, folio); + folio_release_kmap(folio, de); + if (err) + goto out; + + inode_set_ctime_to_ts(inode, inode_get_ctime(dir)); + + if (inode->i_nlink) + inode_dec_link_count(inode); + + err = 0; +out: + return err; +} + +static int ext2_rmdir (struct inode * dir, struct dentry *dentry) +{ + struct inode * inode = d_inode(dentry); + int err = -ENOTEMPTY; + + if (ext2_empty_dir(inode)) { + err = ext2_unlink(dir, dentry); + if (!err) { + inode->i_size = 0; + inode_dec_link_count(inode); + inode_dec_link_count(dir); + } + } + return err; +} + +static int ext2_rename (struct mnt_idmap * idmap, + struct inode * old_dir, struct dentry * old_dentry, + struct inode * new_dir, struct dentry * new_dentry, + unsigned int flags) +{ + struct inode * old_inode = d_inode(old_dentry); + struct inode * new_inode = d_inode(new_dentry); + struct folio *dir_folio = NULL; + struct ext2_dir_entry_2 * dir_de = NULL; + struct folio * old_folio; + struct ext2_dir_entry_2 * old_de; + bool old_is_dir = S_ISDIR(old_inode->i_mode); + int err; + + if (flags & ~RENAME_NOREPLACE) + return -EINVAL; + + err = dquot_initialize(old_dir); + if (err) + return err; + + err = dquot_initialize(new_dir); + if (err) + return err; + + old_de = ext2_find_entry(old_dir, &old_dentry->d_name, &old_folio); + if (IS_ERR(old_de)) + return PTR_ERR(old_de); + + if (old_is_dir && old_dir != new_dir) { + err = -EIO; + dir_de = ext2_dotdot(old_inode, &dir_folio); + if (!dir_de) + goto out_old; + } + + if (new_inode) { + struct folio *new_folio; + struct ext2_dir_entry_2 *new_de; + + err = -ENOTEMPTY; + if (old_is_dir && !ext2_empty_dir(new_inode)) + goto out_dir; + + new_de = ext2_find_entry(new_dir, &new_dentry->d_name, + &new_folio); + if (IS_ERR(new_de)) { + err = PTR_ERR(new_de); + goto out_dir; + } + err = ext2_set_link(new_dir, new_de, new_folio, old_inode, true); + folio_release_kmap(new_folio, new_de); + if (err) + goto out_dir; + inode_set_ctime_current(new_inode); + if (old_is_dir) + drop_nlink(new_inode); + inode_dec_link_count(new_inode); + } else { + err = ext2_add_link(new_dentry, old_inode); + if (err) + goto out_dir; + if (old_is_dir) + inode_inc_link_count(new_dir); + } + + /* + * Like most other Unix systems, set the ctime for inodes on a + * rename. + */ + inode_set_ctime_current(old_inode); + mark_inode_dirty(old_inode); + + err = ext2_delete_entry(old_de, old_folio); + if (!err && old_is_dir) { + if (old_dir != new_dir) + err = ext2_set_link(old_inode, dir_de, dir_folio, + new_dir, false); + + inode_dec_link_count(old_dir); + } +out_dir: + if (dir_de) + folio_release_kmap(dir_folio, dir_de); +out_old: + folio_release_kmap(old_folio, old_de); + return err; +} + +const struct inode_operations ext2_dir_inode_operations = { + .create = ext2_create, + .lookup = ext2_lookup, + .link = ext2_link, + .unlink = ext2_unlink, + .symlink = ext2_symlink, + .mkdir = ext2_mkdir, + .rmdir = ext2_rmdir, + .mknod = ext2_mknod, + .rename = ext2_rename, + .listxattr = ext2_listxattr, + .getattr = ext2_getattr, + .setattr = ext2_setattr, + .get_inode_acl = ext2_get_acl, + .set_acl = ext2_set_acl, + .tmpfile = ext2_tmpfile, + .fileattr_get = ext2_fileattr_get, + .fileattr_set = ext2_fileattr_set, +}; + +const struct inode_operations ext2_special_inode_operations = { + .listxattr = ext2_listxattr, + .getattr = ext2_getattr, + .setattr = ext2_setattr, + .get_inode_acl = ext2_get_acl, + .set_acl = ext2_set_acl, +}; -- cgit v1.3.1