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BUG: KMSAN: uninit-value in copyout lib/iov_iter.c:140 [inline]
BUG: KMSAN: uninit-value in copy_page_to_iter_iovec lib/iov_iter.c:212 [inline]
BUG: KMSAN: uninit-value in copy_page_to_iter+0x754/0x1b70 lib/iov_iter.c:716
CPU: 0 PID: 16070 Comm: syz-executor1 Not tainted 4.17.0-rc5+ #2
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x185/0x1d0 lib/dump_stack.c:113
 kmsan_report+0x149/0x260 mm/kmsan/kmsan.c:1084
 kmsan_internal_check_memory+0x179/0x1e0 mm/kmsan/kmsan.c:1196
 kmsan_copy_to_user+0x75/0x160 mm/kmsan/kmsan.c:1219
 copyout lib/iov_iter.c:140 [inline]
 copy_page_to_iter_iovec lib/iov_iter.c:212 [inline]
 copy_page_to_iter+0x754/0x1b70 lib/iov_iter.c:716
 generic_file_buffered_read mm/filemap.c:2185 [inline]
 generic_file_read_iter+0x2ef8/0x44d0 mm/filemap.c:2362
 ext4_file_read_iter+0x30f/0x520 include/linux/fs.h:728
 call_read_iter include/linux/fs.h:1778 [inline]
 new_sync_read fs/read_write.c:406 [inline]
 __vfs_read+0x775/0x9d0 fs/read_write.c:418
 vfs_read+0x36c/0x6b0 fs/read_write.c:452
 ksys_read fs/read_write.c:578 [inline]
 __do_sys_read fs/read_write.c:588 [inline]
 __se_sys_read fs/read_write.c:586 [inline]
 __x64_sys_read+0x1bf/0x3e0 fs/read_write.c:586
 do_syscall_64+0x15b/0x230 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x455a09
RSP: 002b:00007f2abaf89c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f2abaf8a6d4 RCX: 0000000000455a09
RDX: 00000000c3c2487f RSI: 0000000020000400 RDI: 0000000000000013
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000566 R14: 00000000006fd230 R15: 0000000000000000

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:279 [inline]
 kmsan_alloc_meta_for_pages+0x161/0x3a0 mm/kmsan/kmsan.c:815
 kmsan_alloc_page+0x82/0xe0 mm/kmsan/kmsan.c:885
 __alloc_pages_nodemask+0xf7b/0x5cc0 mm/page_alloc.c:4402
 alloc_pages_current+0x6b1/0x970 mm/mempolicy.c:2093
 alloc_pages include/linux/gfp.h:494 [inline]
 __page_cache_alloc+0x95/0x320 mm/filemap.c:946
 pagecache_get_page+0x52b/0x1450 mm/filemap.c:1577
 find_or_create_page include/linux/pagemap.h:322 [inline]
 __ext4_block_zero_page_range fs/ext4/inode.c:3987 [inline]
 ext4_block_zero_page_range+0x361/0x2280 fs/ext4/inode.c:4091
 ext4_block_truncate_page fs/ext4/inode.c:4115 [inline]
 ext4_truncate+0x1374/0x1dd0 fs/ext4/inode.c:4443
 ext4_setattr+0x38b6/0x3ae0 fs/ext4/inode.c:5532
 notify_change+0x1722/0x1b10 fs/attr.c:313
 do_truncate fs/open.c:63 [inline]
 do_sys_ftruncate+0xa1a/0xad0 fs/open.c:205
 __do_sys_ftruncate fs/open.c:215 [inline]
 __se_sys_ftruncate fs/open.c:213 [inline]
 __x64_sys_ftruncate+0x9e/0xd0 fs/open.c:213
 do_syscall_64+0x15b/0x230 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Bytes 0-3 of 4 are uninitialized
Memory access starts at ffff880119153000
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