Dear Linux folks,
Enabling the undefined behavior sanitizer and building GNU/Linux
4.18-rc5+ (with some unrelated commits) with GCC 8.1.0 from Debian
Sid/unstable, the warning below is shown.
[ 0.629629] ================================================================================
[ 0.629765] UBSAN: Undefined behaviour in fs/ext4/readpage.c:129:13
[ 0.629814] member access within null pointer of type 'struct page'
[ 0.629867] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.18.0-rc5-00316-g4864b68cedf2 #104
[ 0.629869] Hardware name: ASROCK E350M1/E350M1, BIOS TIMELESS 01/01/1970
[ 0.629872] Call Trace:
[ 0.629886] dump_stack+0x55/0x89
[ 0.629892] ubsan_epilogue+0xb/0x33
[ 0.629897] handle_null_ptr_deref+0x7f/0x90
[ 0.629901] __ubsan_handle_type_mismatch_v1+0x55/0x60
[ 0.629907] ext4_mpage_readpages+0xe9a/0xf4a
[ 0.629914] ? find_get_entry+0x3c/0x230
[ 0.629919] ? __alloc_pages_nodemask+0x10d/0x1710
[ 0.629925] ext4_readpages+0x50/0xa0
[ 0.629928] ? ext4_bmap+0x240/0x240
[ 0.629932] read_pages+0x5f/0x230
[ 0.629936] __do_page_cache_readahead+0x1cb/0x260
[ 0.629941] ? __radix_tree_lookup+0x36/0xe0
[ 0.629945] ondemand_readahead+0x1be/0x330
[ 0.629949] page_cache_sync_readahead+0x4f/0x90
[ 0.629953] generic_file_read_iter+0x624/0x1270
[ 0.629960] ? ext4_xattr_security_set+0x30/0x30
[ 0.629964] ext4_file_read_iter+0x86/0x200
[ 0.629969] __vfs_read+0x192/0x2c0
[ 0.629974] vfs_read+0x8e/0x210
[ 0.629978] kernel_read+0x6d/0x100
[ 0.629982] prepare_binprm+0x231/0x3e0
[ 0.629986] __do_execve_file+0x607/0xee0
[ 0.629991] ? kmem_cache_alloc+0x184/0x3e0
[ 0.629995] do_execve+0x2c/0x30
[ 0.629999] run_init_process+0x31/0x36
[ 0.630004] ? rest_init+0x29/0xf6
[ 0.630007] kernel_init+0xd8/0x152
[ 0.630009] ? rest_init+0xf6/0xf6
[ 0.630012] ret_from_fork+0x1c/0x38
[ 0.630016] ================================================================================
Bug report #199635 [1] already exists for the issue, but I assume you
prefer to use the mailing list.
Kind regards,
Paul
[1]: https://bugzilla.kernel.org/show_bug.cgi?id=199635
