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authorAl Viro <viro@zeniv.linux.org.uk>2020-01-19 19:44:51 +0300
committerAl Viro <viro@zeniv.linux.org.uk>2020-03-14 04:08:19 +0300
commitb4c0353693d22f9dcfa4757262dab0aab8376d19 (patch)
tree1449c03091a907b391db729c0b29ac98b5129e36 /include/linux/namei.h
parentad6cc4c338f4e5124c29971ea749073a697063a1 (diff)
downloadlinux-b4c0353693d22f9dcfa4757262dab0aab8376d19.tar.xz
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>
Diffstat (limited to 'include/linux/namei.h')
-rw-r--r--include/linux/namei.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/namei.h b/include/linux/namei.h
index d9576a051808..a4bb992623c4 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -15,7 +15,7 @@ enum { MAX_NESTED_LINKS = 8 };
/*
* Type of the last component on LOOKUP_PARENT
*/
-enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
+enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT};
/* pathwalk mode */
#define LOOKUP_FOLLOW 0x0001 /* follow links at the end */