Ping? I have written an fstest for this fix, but since it generates a corrupted image that crashes the kernel I'd rather have the bug fixed before submitting it. Cheers, -- Luís Luís Henriques <lhenriques@xxxxxxx> writes: > When walking through an inode extents, the ext4_ext_binsearch_idx() function > assumes that the extent header has been previously validated. However, there > are no checks that verify that the number of entries (eh->eh_entries) is > non-zero when depth is > 0. And this will lead to problems because the > EXT_FIRST_INDEX() and EXT_LAST_INDEX() will return garbage and result in this: > > [ 135.245946] ------------[ cut here ]------------ > [ 135.247579] kernel BUG at fs/ext4/extents.c:2258! > [ 135.249045] invalid opcode: 0000 [#1] PREEMPT SMP > [ 135.250320] CPU: 2 PID: 238 Comm: tmp118 Not tainted 5.19.0-rc8+ #4 > [ 135.252067] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.15.0-0-g2dd4b9b-rebuilt.opensuse.org 04/01/2014 > [ 135.255065] RIP: 0010:ext4_ext_map_blocks+0xc20/0xcb0 > [ 135.256475] Code: > [ 135.261433] RSP: 0018:ffffc900005939f8 EFLAGS: 00010246 > [ 135.262847] RAX: 0000000000000024 RBX: ffffc90000593b70 RCX: 0000000000000023 > [ 135.264765] RDX: ffff8880038e5f10 RSI: 0000000000000003 RDI: ffff8880046e922c > [ 135.266670] RBP: ffff8880046e9348 R08: 0000000000000001 R09: ffff888002ca580c > [ 135.268576] R10: 0000000000002602 R11: 0000000000000000 R12: 0000000000000024 > [ 135.270477] R13: 0000000000000000 R14: 0000000000000024 R15: 0000000000000000 > [ 135.272394] FS: 00007fdabdc56740(0000) GS:ffff88807dd00000(0000) knlGS:0000000000000000 > [ 135.274510] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 135.276075] CR2: 00007ffc26bd4f00 CR3: 0000000006261004 CR4: 0000000000170ea0 > [ 135.277952] Call Trace: > [ 135.278635] <TASK> > [ 135.279247] ? preempt_count_add+0x6d/0xa0 > [ 135.280358] ? percpu_counter_add_batch+0x55/0xb0 > [ 135.281612] ? _raw_read_unlock+0x18/0x30 > [ 135.282704] ext4_map_blocks+0x294/0x5a0 > [ 135.283745] ? xa_load+0x6f/0xa0 > [ 135.284562] ext4_mpage_readpages+0x3d6/0x770 > [ 135.285646] read_pages+0x67/0x1d0 > [ 135.286492] ? folio_add_lru+0x51/0x80 > [ 135.287441] page_cache_ra_unbounded+0x124/0x170 > [ 135.288510] filemap_get_pages+0x23d/0x5a0 > [ 135.289457] ? path_openat+0xa72/0xdd0 > [ 135.290332] filemap_read+0xbf/0x300 > [ 135.291158] ? _raw_spin_lock_irqsave+0x17/0x40 > [ 135.292192] new_sync_read+0x103/0x170 > [ 135.293014] vfs_read+0x15d/0x180 > [ 135.293745] ksys_read+0xa1/0xe0 > [ 135.294461] do_syscall_64+0x3c/0x80 > [ 135.295284] entry_SYSCALL_64_after_hwframe+0x46/0xb0 > > This patch simply adds an extra check in __ext4_ext_check(), verifying that > eh_entries is not 0 when eh_depth is > 0. > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=215941 > Link: https://bugzilla.kernel.org/show_bug.cgi?id=216283 > Cc: Baokun Li <libaokun1@xxxxxxxxxx> > Signed-off-by: Luís Henriques <lhenriques@xxxxxxx> > --- > fs/ext4/extents.c | 4 ++++ > 1 file changed, 4 insertions(+) > > Changes since v3: > - Fixed typo (I had 'eh_depth' instead of 'depth') > > Changes since v2: > - Dropped usage of le16_to_cpu() because we're comparing values against 0 > - Use 'depth' instead of 'eh->eh_depth' because we've checked earlier that > both have the same value. > > > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > index c148bb97b527..5235974126bd 100644 > --- a/fs/ext4/extents.c > +++ b/fs/ext4/extents.c > @@ -460,6 +460,10 @@ static int __ext4_ext_check(const char *function, unsigned int line, > error_msg = "invalid eh_entries"; > goto corrupted; > } > + if (unlikely((eh->eh_entries == 0) && (depth > 0))) { > + error_msg = "eh_entries is 0 but eh_depth is > 0"; > + goto corrupted; > + } > if (!ext4_valid_extent_entries(inode, eh, lblk, &pblk, depth)) { > error_msg = "invalid extent entries"; > goto corrupted;
