linux/fs/afs
David Howells 3f4aa98181 afs: Fix EOF corruption
When doing a partial writeback, afs_write_back_from_locked_page() may
generate an FS.StoreData RPC request that writes out part of a file when a
file has been constructed from pieces by doing seek, write, seek, write,
... as is done by ld.

The FS.StoreData RPC is given the current i_size as the file length, but
the server basically ignores it unless the data length is 0 (in which case
it's just a truncate operation).  The revised file length returned in the
result of the RPC may then not reflect what we suggested - and this leads
to i_size getting moved backwards - which causes issues later.

Fix the client to take account of this by ignoring the returned file size
unless the data version number jumped unexpectedly - in which case we're
going to have to clear the pagecache and reload anyway.

This can be observed when doing a kernel build on an AFS mount.  The
following pair of commands produce the issue:

  ld -m elf_x86_64 -z max-page-size=0x200000 --emit-relocs \
      -T arch/x86/realmode/rm/realmode.lds \
      arch/x86/realmode/rm/header.o \
      arch/x86/realmode/rm/trampoline_64.o \
      arch/x86/realmode/rm/stack.o \
      arch/x86/realmode/rm/reboot.o \
      -o arch/x86/realmode/rm/realmode.elf
  arch/x86/tools/relocs --realmode \
      arch/x86/realmode/rm/realmode.elf \
      >arch/x86/realmode/rm/realmode.relocs

This results in the latter giving:

	Cannot read ELF section headers 0/18: Success

as the realmode.elf file got corrupted.

The sequence of events can also be driven with:

	xfs_io -t -f \
		-c "pwrite -S 0x58 0 0x58" \
		-c "pwrite -S 0x59 10000 1000" \
		-c "close" \
		/afs/example.com/scratch/a

Fixes: 31143d5d51 ("AFS: implement basic file write support")
Signed-off-by: David Howells <dhowells@redhat.com>
2020-06-15 15:41:02 +01:00
..
addr_list.c afs: Use kfree_rcu() instead of casting kfree() to rcu_callback_t 2020-03-13 10:47:33 -07:00
afs_cm.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
afs_fs.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
afs_vl.h afs: Implement client support for the YFSVL.GetCellName RPC op 2020-06-04 15:37:57 +01:00
afs.h afs: Implement client support for the YFSVL.GetCellName RPC op 2020-06-04 15:37:57 +01:00
cache.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
callback.c afs: Fix the by-UUID server tree to allow servers with the same UUID 2020-06-04 15:37:57 +01:00
cell.c afs: Reorganise volume and server trees to be rooted on the cell 2020-06-04 15:37:57 +01:00
cmservice.c afs: Fix handling of CB.ProbeUuid cache manager op 2020-06-04 15:37:57 +01:00
dir_edit.c afs: Remove set but not used variables 'before', 'after' 2019-11-21 20:36:00 +00:00
dir_silly.c afs: Build an abstraction around an "operation" concept 2020-06-04 15:37:17 +01:00
dir.c afs: Fix debugging statements with %px to be %p 2020-06-09 18:17:14 +01:00
dynroot.c afs: Build an abstraction around an "operation" concept 2020-06-04 15:37:17 +01:00
file.c afs: Build an abstraction around an "operation" concept 2020-06-04 15:37:17 +01:00
flock.c afs: Fix file locking 2020-06-09 15:22:06 +01:00
fs_operation.c afs: Reorganise volume and server trees to be rooted on the cell 2020-06-04 15:37:57 +01:00
fs_probe.c afs: Adjust the fileserver rotation algorithm to reprobe/retry more quickly 2020-06-04 15:37:58 +01:00
fsclient.c afs: Reorganise volume and server trees to be rooted on the cell 2020-06-04 15:37:57 +01:00
inode.c afs: Fix EOF corruption 2020-06-15 15:41:02 +01:00
internal.h afs: Make afs_zap_data() static 2020-06-09 18:17:14 +01:00
Kconfig docs: filesystems: fix renamed references 2020-04-20 15:45:22 -06:00
main.c afs: Detect cell aliases 1 - Cells with root volumes 2020-06-04 15:37:57 +01:00
Makefile afs: Detect cell aliases 1 - Cells with root volumes 2020-06-04 15:37:57 +01:00
misc.c AFS development 2019-07-10 20:55:33 -07:00
mntpt.c afs: Fix mountpoint parsing 2019-12-11 16:56:54 +00:00
proc.c afs: Fix memory leak in afs_put_sysnames() 2020-06-09 15:22:06 +01:00
protocol_uae.h afs: Add support for the UAE error table 2019-06-28 18:37:53 +01:00
protocol_yfs.h afs: Implement client support for the YFSVL.GetCellName RPC op 2020-06-04 15:37:57 +01:00
rotate.c afs: Adjust the fileserver rotation algorithm to reprobe/retry more quickly 2020-06-04 15:37:58 +01:00
rxrpc.c AFS Changes 2020-06-05 16:26:36 -07:00
security.c afs: Reorganise volume and server trees to be rooted on the cell 2020-06-04 15:37:57 +01:00
server_list.c afs: Reorganise volume and server trees to be rooted on the cell 2020-06-04 15:37:57 +01:00
server.c afs: Don't use probe running state to make decisions outside probe code 2020-06-04 15:37:58 +01:00
super.c afs: Fix afs_statfs() to not let the values go below zero 2020-06-04 15:37:58 +01:00
vl_alias.c afs: Fix debugging statements with %px to be %p 2020-06-09 18:17:14 +01:00
vl_list.c fs/afs: Replace rcu_swap_protected() with rcu_replace_pointer() 2019-10-30 08:44:27 -07:00
vl_probe.c rxrpc: Fix the excessive initial retransmission timeout 2020-05-11 16:42:28 +01:00
vl_rotate.c afs: Detect cell aliases 3 - YFS Cells with a canonical cell name op 2020-06-04 15:37:57 +01:00
vlclient.c afs: Implement client support for the YFSVL.GetCellName RPC op 2020-06-04 15:37:57 +01:00
volume.c afs: Reorganise volume and server trees to be rooted on the cell 2020-06-04 15:37:57 +01:00
write.c afs: afs_write_end() should change i_size under the right lock 2020-06-15 15:41:02 +01:00
xattr.c afs: Build an abstraction around an "operation" concept 2020-06-04 15:37:17 +01:00
xdr_fs.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
yfsclient.c afs: Remove afs_zero_fid as it's not used 2020-06-09 18:17:14 +01:00