Use get_kernel_nofault() to safely access inode and related structures (superblock, file_system_type) to avoid crashing when the inode pointer is invalid. This allows the same pattern as dump_mapping(). Note: The original access method for i_state and i_count is preserved, as get_kernel_nofault() is unnecessary once the inode structure is verified accessible. Reviewed-by: Jan Kara Signed-off-by: Yuto Ohnuki --- Changes in v3: - Avoided pr_warn duplication for long-term maintainability. - Changed "invalid inode" to "unreadable inode", and clearly denote the situation where sb is unreadable as suggested by Mateusz Guzik. - Added passed reason to all pr_warn outputs. - Used %# format specifier for printing hex values, verified to work as expected. - Link to v2: https://lore.kernel.org/linux-fsdevel/20260109154019.74717-1-ytohnuki@amazon.com/ Changes in v2: - Merged NULL inode->i_sb check with invalid sb check as pointed out by Jan Kara. - Link to v1: https://lore.kernel.org/linux-fsdevel/20260101165304.34516-1-ytohnuki@amazon.com/ --- fs/inode.c | 47 ++++++++++++++++++++++++++++++++++------------- 1 file changed, 34 insertions(+), 13 deletions(-) diff --git a/fs/inode.c b/fs/inode.c index 521383223d8a..440ae05f9df5 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -2984,24 +2984,45 @@ umode_t mode_strip_sgid(struct mnt_idmap *idmap, EXPORT_SYMBOL(mode_strip_sgid); #ifdef CONFIG_DEBUG_VFS -/* - * Dump an inode. - * - * TODO: add a proper inode dumping routine, this is a stub to get debug off the - * ground. +/** + * dump_inode - dump an inode. + * @inode: inode to dump + * @reason: reason for dumping * - * TODO: handle getting to fs type with get_kernel_nofault()? - * See dump_mapping() above. + * If inode is an invalid pointer, we don't want to crash accessing it, + * so probe everything depending on it carefully with get_kernel_nofault(). */ void dump_inode(struct inode *inode, const char *reason) { - struct super_block *sb = inode->i_sb; + struct super_block *sb; + struct file_system_type *s_type; + const char *fs_name_ptr; + char fs_name[32] = {}; + umode_t mode; + unsigned short opflags; + unsigned int flags; + unsigned int state; + int count; + + if (get_kernel_nofault(sb, &inode->i_sb) || + get_kernel_nofault(mode, &inode->i_mode) || + get_kernel_nofault(opflags, &inode->i_opflags) || + get_kernel_nofault(flags, &inode->i_flags)) { + pr_warn("%s: unreadable inode:%px\n", reason, inode); + return; + } - pr_warn("%s encountered for inode %px\n" - "fs %s mode %ho opflags 0x%hx flags 0x%x state 0x%x count %d\n", - reason, inode, sb->s_type->name, inode->i_mode, inode->i_opflags, - inode->i_flags, inode_state_read_once(inode), atomic_read(&inode->i_count)); -} + state = inode_state_read_once(inode); + count = atomic_read(&inode->i_count); + if (!sb || + get_kernel_nofault(s_type, &sb->s_type) || !s_type || + get_kernel_nofault(fs_name_ptr, &s_type->name) || !fs_name_ptr || + strncpy_from_kernel_nofault(fs_name, fs_name_ptr, sizeof(fs_name) - 1) < 0) + strscpy(fs_name, ""); + + pr_warn("%s: inode:%px fs:%s mode:%ho opflags:%#x flags:%#x state:%#x count:%d\n", + reason, inode, fs_name, mode, opflags, flags, state, count); +} EXPORT_SYMBOL(dump_inode); #endif -- 2.50.1 Amazon Web Services EMEA SARL, 38 avenue John F. Kennedy, L-1855 Luxembourg, R.C.S. Luxembourg B186284 Amazon Web Services EMEA SARL, Irish Branch, One Burlington Plaza, Burlington Road, Dublin 4, Ireland, branch registration number 908705