linux/include
Al Viro b4c0353693 sanitize handling of nd->last_type, kill LAST_BIND
->last_type values are set in 3 places: path_init() (sets to LAST_ROOT),
link_path_walk (LAST_NORM/DOT/DOTDOT) and pick_link (LAST_BIND).

The are checked in walk_component(), lookup_last() and do_last().
They also get copied to the caller by filename_parentat().  In the last
3 cases the value is what we had at the return from link_path_walk().
In case of walk_component() it's either directly downstream from
assignment in link_path_walk() or, when called by lookup_last(), the
value we have at the return from link_path_walk().

The value at the entry into link_path_walk() can survive to return only
if the pathname contains nothing but slashes.  Note that pick_link()
never returns such - pure jumps are handled directly.  So for the calls
of link_path_walk() for trailing symlinks it does not matter what value
had been there at the entry; the value at the return won't depend upon it.

There are 3 call chains that might have pick_link() storing LAST_BIND:

1) pick_link() from step_into() from walk_component() from
link_path_walk().  In that case we will either be parsing the next
component immediately after return into link_path_walk(), which will
overwrite the ->last_type before anyone has a chance to look at it,
or we'll fail, in which case nobody will be looking at ->last_type at all.

2) pick_link() from step_into() from walk_component() from lookup_last().
The value is never looked at due to the above; it won't affect the value
seen at return from any link_path_walk().

3) pick_link() from step_into() from do_last().  Ditto.

In other words, assignemnt in pick_link() is pointless, and so is
LAST_BIND itself; nothing ever looks at that value.  Kill it off.
And make link_path_walk() _always_ assign ->last_type - in the only
case when the value at the entry might survive to the return that value
is always LAST_ROOT, inherited from path_init().  Move that assignment
from path_init() into the beginning of link_path_walk(), to consolidate
the things.

Historical note: LAST_BIND used to be used for the kludge with trailing
pure jump symlinks (extra iteration through the top-level loop).
No point keeping it anymore...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2020-03-13 21:08:19 -04:00
..
acpi
asm-generic Microblaze patches for 5.6-rc1 2020-02-04 11:58:07 +00:00
clocksource
crypto
drm drm/amdgpu: fix doc by clarifying sched_list definition 2020-01-27 16:46:44 -05:00
dt-bindings ARM: SoC: late updates 2020-02-08 14:17:27 -08:00
keys
kunit
kvm
linux sanitize handling of nd->last_type, kill LAST_BIND 2020-03-13 21:08:19 -04:00
math-emu
media
misc
net bonding/alb: properly access headers in bond_alb_xmit() 2020-02-05 14:28:09 +01:00
pcmcia
ras
rdma RDMA/core: Make the entire API tree static 2020-01-30 16:28:52 -04:00
scsi
soc ARM: SoC-related driver updates 2020-02-08 14:04:19 -08:00
sound ARM: Device-tree updates 2020-02-08 13:58:44 -08:00
target
trace ARM: SoC-related driver updates 2020-02-08 14:04:19 -08:00
uapi fs: New zonefs file system 2020-02-09 15:51:46 -08:00
vdso
video
xen xen: branch for v5.6-rc1 2020-02-05 17:44:14 +00:00