From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> Subject: mm/debug.c: do not dereference i_ino blindly __dump_page() checks i_dentry is fetchable and i_ino is earlier in the struct than i_ino, so it ought to work fine, but it's possible that struct randomisation has reordered i_ino after i_dentry and the pointer is just wild enough that i_dentry is fetchable and i_ino isn't. Also print the inode number if the dentry is invalid. Link: https://lkml.kernel.org/r/20200819185710.28180-1-willy@xxxxxxxxxxxxx Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Reported-by: Vlastimil Babka <vbabka@xxxxxxx> Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx> Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/debug.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) --- a/mm/debug.c~mm-debug-do-not-dereference-i_ino-blindly +++ a/mm/debug.c @@ -120,6 +120,7 @@ void __dump_page(struct page *page, cons struct hlist_node *dentry_first; struct dentry *dentry_ptr; struct dentry dentry; + unsigned long ino; /* * mapping can be invalid pointer and we don't want to crash @@ -136,21 +137,22 @@ void __dump_page(struct page *page, cons goto out_mapping; } - if (get_kernel_nofault(dentry_first, &host->i_dentry.first)) { + if (get_kernel_nofault(dentry_first, &host->i_dentry.first) || + get_kernel_nofault(ino, &host->i_ino)) { pr_warn("aops:%ps with invalid host inode %px\n", a_ops, host); goto out_mapping; } if (!dentry_first) { - pr_warn("aops:%ps ino:%lx\n", a_ops, host->i_ino); + pr_warn("aops:%ps ino:%lx\n", a_ops, ino); goto out_mapping; } dentry_ptr = container_of(dentry_first, struct dentry, d_u.d_alias); if (get_kernel_nofault(dentry, dentry_ptr)) { - pr_warn("aops:%ps with invalid dentry %px\n", a_ops, - dentry_ptr); + pr_warn("aops:%ps ino:%lx with invalid dentry %px\n", + a_ops, ino, dentry_ptr); } else { /* * if dentry is corrupted, the %pd handler may still @@ -158,7 +160,7 @@ void __dump_page(struct page *page, cons * corrupted struct page */ pr_warn("aops:%ps ino:%lx dentry name:\"%pd\"\n", - a_ops, host->i_ino, &dentry); + a_ops, ino, &dentry); } } out_mapping: _
