diff options
| author | Johannes Thumshirn <johannes.thumshirn@wdc.com> | 2020-10-22 23:05:05 +0900 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2020-10-27 15:11:37 +0100 |
| commit | 0425e7badbdcb6e47109bfdfe494d86217e29009 (patch) | |
| tree | 9c5ed26d947ad44825a694c38db746687abe35b4 | |
| parent | 49d11bead7d596e031fbd34051d8765587cd645b (diff) | |
btrfs: don't fallback to buffered read if we don't need to
Since we switched to the iomap infrastructure in b5ff9f1a96e8f ("btrfs:
switch to iomap for direct IO") we're calling generic_file_buffered_read()
directly and not via generic_file_read_iter() anymore.
If the read could read everything there is no need to bother calling
generic_file_buffered_read(), like it is handled in
generic_file_read_iter().
If we call generic_file_buffered_read() in this case we can hit a
situation where we do an invalid readahead and cause this UBSAN splat
in fstest generic/091:
run fstests generic/091 at 2020-10-21 10:52:32
================================================================================
UBSAN: shift-out-of-bounds in ./include/linux/log2.h:57:13
shift exponent 64 is too large for 64-bit type 'long unsigned int'
CPU: 0 PID: 656 Comm: fsx Not tainted 5.9.0-rc7+ #821
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4-rebuilt.opensuse.org 04/01/2014
Call Trace:
__dump_stack lib/dump_stack.c:77
dump_stack+0x57/0x70 lib/dump_stack.c:118
ubsan_epilogue+0x5/0x40 lib/ubsan.c:148
__ubsan_handle_shift_out_of_bounds.cold+0x61/0xe9 lib/ubsan.c:395
__roundup_pow_of_two ./include/linux/log2.h:57
get_init_ra_size mm/readahead.c:318
ondemand_readahead.cold+0x16/0x2c mm/readahead.c:530
generic_file_buffered_read+0x3ac/0x840 mm/filemap.c:2199
call_read_iter ./include/linux/fs.h:1876
new_sync_read+0x102/0x180 fs/read_write.c:415
vfs_read+0x11c/0x1a0 fs/read_write.c:481
ksys_read+0x4f/0xc0 fs/read_write.c:615
do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9 arch/x86/entry/entry_64.S:118
RIP: 0033:0x7fe87fee992e
RSP: 002b:00007ffe01605278 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 000000000004f000 RCX: 00007fe87fee992e
RDX: 0000000000004000 RSI: 0000000001677000 RDI: 0000000000000003
RBP: 000000000004f000 R08: 0000000000004000 R09: 000000000004f000
R10: 0000000000053000 R11: 0000000000000246 R12: 0000000000004000
R13: 0000000000000000 R14: 000000000007a120 R15: 0000000000000000
================================================================================
BTRFS info (device nullb0): has skinny extents
BTRFS info (device nullb0): ZONED mode enabled, zone size 268435456 B
BTRFS info (device nullb0): enabling ssd optimizations
Fixes: f85781fb505e ("btrfs: switch to iomap for direct IO")
Reviewed-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
| -rw-r--r-- | fs/btrfs/file.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 0ff659455b1e..87355a38a654 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -3628,7 +3628,8 @@ static ssize_t btrfs_file_read_iter(struct kiocb *iocb, struct iov_iter *to) inode_lock_shared(inode); ret = btrfs_direct_IO(iocb, to); inode_unlock_shared(inode); - if (ret < 0) + if (ret < 0 || !iov_iter_count(to) || + iocb->ki_pos >= i_size_read(file_inode(iocb->ki_filp))) return ret; } |