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As Dan Carpenter as below: The patch df634f444ee9: "f2fs: use rb_*_cached friends" from Oct 4, 2018, leads to the following static checker warning: fs/f2fs/extent_cache.c:606 f2fs_update_extent_tree_range() error: uninitialized symbol 'leftmost'. And also Eric Biggers, and Kyungtae Kim reported, there is an UBSAN warning described as below: We report a bug in linux-4.20.2: "UBSAN: Undefined behaviour in fs/f2fs/extent_cache.c" kernel config: https://kt0755.github.io/etc/config_v4.20_stable repro: https://kt0755.github.io/etc/repro.4a3e7.c (f2fs is mounted on /mnt/f2fs/) This arose in f2fs_update_extent_tree_range (fs/f2fs/extent_cache.c:605). It seems that, for some reason, its last argument became "24" although that was supposed to be bool type. ========================================= UBSAN: Undefined behaviour in fs/f2fs/extent_cache.c:605:4 load of value 24 is not a valid value for type '_Bool' CPU: 0 PID: 6774 Comm: syz-executor5 Not tainted 4.20.2 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0xb1/0x118 lib/dump_stack.c:113 ubsan_epilogue+0x12/0x94 lib/ubsan.c:159 __ubsan_handle_load_invalid_value+0x17a/0x1be lib/ubsan.c:457 f2fs_update_extent_tree_range+0x1d4a/0x1d50 fs/f2fs/extent_cache.c:605 f2fs_update_extent_cache+0x2b6/0x350 fs/f2fs/extent_cache.c:804 f2fs_update_data_blkaddr+0x61/0x70 fs/f2fs/data.c:656 f2fs_outplace_write_data+0x1d6/0x4b0 fs/f2fs/segment.c:3140 f2fs_convert_inline_page+0x86d/0x2060 fs/f2fs/inline.c:163 f2fs_convert_inline_inode+0x6b5/0xad0 fs/f2fs/inline.c:208 f2fs_preallocate_blocks+0x78b/0xb00 fs/f2fs/data.c:982 f2fs_file_write_iter+0x31b/0xf40 fs/f2fs/file.c:3062 call_write_iter include/linux/fs.h:1857 [inline] new_sync_write fs/read_write.c:474 [inline] __vfs_write+0x538/0x6e0 fs/read_write.c:487 vfs_write+0x1b3/0x520 fs/read_write.c:549 ksys_write+0xde/0x1c0 fs/read_write.c:598 __do_sys_write fs/read_write.c:610 [inline] __se_sys_write fs/read_write.c:607 [inline] __x64_sys_write+0x7e/0xc0 fs/read_write.c:607 do_syscall_64+0xbe/0x4f0 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4497b9 Code: e8 8c 9f 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 9b 6b fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f1ea15edc68 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f1ea15ee6cc RCX: 00000000004497b9 RDX: 0000000000001000 RSI: 0000000020000140 RDI: 0000000000000013 RBP: 000000000071bea0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 000000000000bb50 R14: 00000000006f4bf0 R15: 00007f1ea15ee700 ========================================= As I checked, this uninitialized variable won't cause extent cache corruption, but in order to avoid such kind of warning of both UBSAN and smatch, fix to initialize related variable. Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Reported-by: Eric Biggers <ebiggers@google.com> Reported-by: Kyungtae Kim <kt0755@gmail.com> Signed-off-by: Chao Yu <yuchao0@huawei.com> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.