116 lines
4.5 KiB
Diff
116 lines
4.5 KiB
Diff
From: Mikhail Efremov <sem@altlinux.org>
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Date: Wed, 24 Sep 2014 22:14:33 +0400
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Subject: vfs: Don't exchange "short" filenames unconditionally.
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Origin: https://git.kernel.org/linus/d2fa4a8476b911782f7e5167db18770222ac40c3
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Only exchange source and destination filenames
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if flags contain RENAME_EXCHANGE.
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In case if executable file was running and replaced by
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other file /proc/PID/exe should still show correct file name,
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not the old name of the file by which it was replaced.
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The scenario when this bug manifests itself was like this:
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* ALT Linux uses rpm and start-stop-daemon;
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* during a package upgrade rpm creates a temporary file
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for an executable to rename it upon successful unpacking;
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* start-stop-daemon is run subsequently and it obtains
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the (nonexistant) temporary filename via /proc/PID/exe
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thus failing to identify the running process.
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Note that "long" filenames (> DNAiME_INLINE_LEN) are still
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exchanged without RENAME_EXCHANGE and this behaviour exists
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long enough (should be fixed too apparently).
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So this patch is just an interim workaround that restores
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behavior for "short" names as it was before changes
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introduced by commit da1ce0670c14 ("vfs: add cross-rename").
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See https://lkml.org/lkml/2014/9/7/6 for details.
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AV: the comments about being more careful with ->d_name.hash
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than with ->d_name.name are from back in 2.3.40s; they
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became obsolete by 2.3.60s, when we started to unhash the
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target instead of swapping hash chain positions followed
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by d_delete() as we used to do when dcache was first
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introduced.
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Acked-by: Miklos Szeredi <mszeredi@suse.cz>
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Cc: Linus Torvalds <torvalds@linux-foundation.org>
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Cc: Alexander Viro <viro@zeniv.linux.org.uk>
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Cc: linux-fsdevel@vger.kernel.org
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Cc: stable@vger.kernel.org
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Fixes: da1ce0670c14 "vfs: add cross-rename"
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Signed-off-by: Mikhail Efremov <sem@altlinux.org>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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[bwh: Backported to 3.16:
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- Adjust context
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- Change __d_materialise_dentry() as well]
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---
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fs/dcache.c | 27 ++++++++++++++++++---------
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1 file changed, 18 insertions(+), 9 deletions(-)
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--- a/fs/dcache.c
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+++ b/fs/dcache.c
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@@ -2401,7 +2401,8 @@ void dentry_update_name_case(struct dent
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}
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EXPORT_SYMBOL(dentry_update_name_case);
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-static void switch_names(struct dentry *dentry, struct dentry *target)
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+static void switch_names(struct dentry *dentry, struct dentry *target,
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+ bool exchange)
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{
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if (dname_external(target)) {
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if (dname_external(dentry)) {
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@@ -2435,6 +2436,12 @@ static void switch_names(struct dentry *
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*/
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unsigned int i;
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BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
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+ if (!exchange) {
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+ memcpy(dentry->d_iname, target->d_name.name,
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+ target->d_name.len + 1);
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+ dentry->d_name.hash_len = target->d_name.hash_len;
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+ return;
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+ }
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for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
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swap(((long *) &dentry->d_iname)[i],
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((long *) &target->d_iname)[i]);
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@@ -2484,12 +2491,15 @@ static void dentry_unlock_parents_for_mo
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* When switching names, the actual string doesn't strictly have to
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* be preserved in the target - because we're dropping the target
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* anyway. As such, we can just do a simple memcpy() to copy over
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- * the new name before we switch.
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- *
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- * Note that we have to be a lot more careful about getting the hash
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- * switched - we have to switch the hash value properly even if it
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- * then no longer matches the actual (corrupted) string of the target.
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- * The hash value has to match the hash queue that the dentry is on..
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+ * the new name before we switch, unless we are going to rehash
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+ * it. Note that if we *do* unhash the target, we are not allowed
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+ * to rehash it without giving it a new name/hash key - whether
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+ * we swap or overwrite the names here, resulting name won't match
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+ * the reality in filesystem; it's only there for d_path() purposes.
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+ * Note that all of this is happening under rename_lock, so the
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+ * any hash lookup seeing it in the middle of manipulations will
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+ * be discarded anyway. So we do not care what happens to the hash
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+ * key in that case.
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*/
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/*
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* __d_move - move a dentry
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@@ -2539,7 +2549,7 @@ static void __d_move(struct dentry *dent
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list_del(&target->d_u.d_child);
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/* Switch the names.. */
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- switch_names(dentry, target);
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+ switch_names(dentry, target, exchange);
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/* ... and switch the parents */
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if (IS_ROOT(dentry)) {
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@@ -2677,7 +2687,7 @@ static void __d_materialise_dentry(struc
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dparent = dentry->d_parent;
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- switch_names(dentry, anon);
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+ switch_names(dentry, anon, false);
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dentry->d_parent = dentry;
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list_del_init(&dentry->d_u.d_child);
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