From 88618feecf44e774e03cf49872567398b0177d25 Mon Sep 17 00:00:00 2001 From: Baokun Li Date: Mon, 15 Nov 2021 09:31:42 +0800 Subject: ubifs: fix slab-out-of-bounds in ubifs_change_lp Hulk Robot reported a KASAN report about slab-out-of-bounds: ================================================================== BUG: KASAN: slab-out-of-bounds in ubifs_change_lp+0x3a9/0x1390 [ubifs] Read of size 8 at addr ffff888101c961f8 by task fsstress/1068 [...] Call Trace: check_memory_region+0x1c1/0x1e0 ubifs_change_lp+0x3a9/0x1390 [ubifs] ubifs_change_one_lp+0x170/0x220 [ubifs] ubifs_garbage_collect+0x7f9/0xda0 [ubifs] ubifs_budget_space+0xfe4/0x1bd0 [ubifs] ubifs_write_begin+0x528/0x10c0 [ubifs] Allocated by task 1068: kmemdup+0x25/0x50 ubifs_lpt_lookup_dirty+0x372/0xb00 [ubifs] ubifs_update_one_lp+0x46/0x260 [ubifs] ubifs_tnc_end_commit+0x98b/0x1720 [ubifs] do_commit+0x6cb/0x1950 [ubifs] ubifs_run_commit+0x15a/0x2b0 [ubifs] ubifs_budget_space+0x1061/0x1bd0 [ubifs] ubifs_write_begin+0x528/0x10c0 [ubifs] [...] ================================================================== In ubifs_garbage_collect(), if ubifs_find_dirty_leb returns an error, lp is an uninitialized variable. But lp.num might be used in the out branch, which is a random value. If the value is -1 or another value that can pass the check, soob may occur in the ubifs_change_lp() in the following procedure. To solve this problem, we initialize lp.lnum to -1, and then initialize it correctly in ubifs_find_dirty_leb, which is not equal to -1, and ubifs_return_leb is executed only when lp.lnum != -1. if find a retained or indexing LEB and continue to next loop, but break before find another LEB, the "taken" flag of this LEB will be cleaned in ubi_return_lebi(). This bug has also been fixed in this patch. Reported-by: Hulk Robot Signed-off-by: Baokun Li Signed-off-by: Richard Weinberger --- fs/ubifs/gc.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'fs/ubifs') diff --git a/fs/ubifs/gc.c b/fs/ubifs/gc.c index dc3e26e9ed7b..05e1eeae8457 100644 --- a/fs/ubifs/gc.c +++ b/fs/ubifs/gc.c @@ -692,6 +692,9 @@ int ubifs_garbage_collect(struct ubifs_info *c, int anyway) for (i = 0; ; i++) { int space_before, space_after; + /* Maybe continue after find and break before find */ + lp.lnum = -1; + cond_resched(); /* Give the commit an opportunity to run */ @@ -843,7 +846,8 @@ out: ubifs_wbuf_sync_nolock(wbuf); ubifs_ro_mode(c, ret); mutex_unlock(&wbuf->io_mutex); - ubifs_return_leb(c, lp.lnum); + if (lp.lnum != -1) + ubifs_return_leb(c, lp.lnum); return ret; } -- cgit v1.2.3