From 22213318af7ae265bc6cd8aef2febbc2d69a2440 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 19 Apr 2014 12:30:58 -0400 Subject: fix races between __d_instantiate() and checks of dentry flags in non-lazy walk we need to be careful about dentry switching from negative to positive - both ->d_flags and ->d_inode are updated, and in some places we might see only one store. The cases where dentry has been obtained by dcache lookup with ->i_mutex held on parent are safe - ->d_lock and ->i_mutex provide all the barriers we need. However, there are several places where we run into trouble: * do_last() fetches ->d_inode, then checks ->d_flags and assumes that inode won't be NULL unless d_is_negative() is true. Race with e.g. creat() - we might have fetched the old value of ->d_inode (still NULL) and new value of ->d_flags (already not DCACHE_MISS_TYPE). Lin Ming has observed and reported the resulting oops. * a bunch of places checks ->d_inode for being non-NULL, then checks ->d_flags for "is it a symlink". Race with symlink(2) in case if our CPU sees ->d_inode update first - we see non-NULL there, but ->d_flags still contains DCACHE_MISS_TYPE instead of DCACHE_SYMLINK_TYPE. Result: false negative on "should we follow link here?", with subsequent unpleasantness. Cc: stable@vger.kernel.org # 3.13 and 3.14 need that one Reported-and-tested-by: Lin Ming Signed-off-by: Al Viro --- fs/dcache.c | 3 +-- fs/namei.c | 6 +++--- 2 files changed, 4 insertions(+), 5 deletions(-) (limited to 'fs') diff --git a/fs/dcache.c b/fs/dcache.c index 40707d88a945..494a9def5dce 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1647,8 +1647,7 @@ static void __d_instantiate(struct dentry *dentry, struct inode *inode) unsigned add_flags = d_flags_for_inode(inode); spin_lock(&dentry->d_lock); - dentry->d_flags &= ~DCACHE_ENTRY_TYPE; - dentry->d_flags |= add_flags; + __d_set_type(dentry, add_flags); if (inode) hlist_add_head(&dentry->d_alias, &inode->i_dentry); dentry->d_inode = inode; diff --git a/fs/namei.c b/fs/namei.c index c6157c894fce..80168273396b 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1542,7 +1542,7 @@ static inline int walk_component(struct nameidata *nd, struct path *path, inode = path->dentry->d_inode; } err = -ENOENT; - if (!inode) + if (!inode || d_is_negative(path->dentry)) goto out_path_put; if (should_follow_link(path->dentry, follow)) { @@ -2249,7 +2249,7 @@ mountpoint_last(struct nameidata *nd, struct path *path) mutex_unlock(&dir->d_inode->i_mutex); done: - if (!dentry->d_inode) { + if (!dentry->d_inode || d_is_negative(dentry)) { error = -ENOENT; dput(dentry); goto out; @@ -2994,7 +2994,7 @@ retry_lookup: finish_lookup: /* we _can_ be in RCU mode here */ error = -ENOENT; - if (d_is_negative(path->dentry)) { + if (!inode || d_is_negative(path->dentry)) { path_to_nameidata(path, nd); goto out; } -- cgit v1.2.3-58-ga151 From 03b3b889e79cdb6b806fc0ba9be0d71c186bbfaa Mon Sep 17 00:00:00 2001 From: Al Viro Date: Tue, 29 Apr 2014 15:45:28 -0400 Subject: fold d_kill() and d_free() Signed-off-by: Al Viro --- fs/dcache.c | 76 +++++++++++++++++++------------------------------------------ 1 file changed, 24 insertions(+), 52 deletions(-) (limited to 'fs') diff --git a/fs/dcache.c b/fs/dcache.c index 494a9def5dce..9b15c5c37277 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -246,23 +246,6 @@ static void __d_free(struct rcu_head *head) kmem_cache_free(dentry_cache, dentry); } -/* - * no locks, please. - */ -static void d_free(struct dentry *dentry) -{ - BUG_ON((int)dentry->d_lockref.count > 0); - this_cpu_dec(nr_dentry); - if (dentry->d_op && dentry->d_op->d_release) - dentry->d_op->d_release(dentry); - - /* if dentry was never visible to RCU, immediate free is OK */ - if (!(dentry->d_flags & DCACHE_RCUACCESS)) - __d_free(&dentry->d_u.d_rcu); - else - call_rcu(&dentry->d_u.d_rcu, __d_free); -} - /** * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups * @dentry: the target dentry @@ -419,40 +402,6 @@ static void dentry_lru_del(struct dentry *dentry) } } -/** - * d_kill - kill dentry and return parent - * @dentry: dentry to kill - * @parent: parent dentry - * - * The dentry must already be unhashed and removed from the LRU. - * - * If this is the root of the dentry tree, return NULL. - * - * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by - * d_kill. - */ -static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent) - __releases(dentry->d_lock) - __releases(parent->d_lock) - __releases(dentry->d_inode->i_lock) -{ - list_del(&dentry->d_u.d_child); - /* - * Inform d_walk() that we are no longer attached to the - * dentry tree - */ - dentry->d_flags |= DCACHE_DENTRY_KILLED; - if (parent) - spin_unlock(&parent->d_lock); - dentry_iput(dentry); - /* - * dentry_iput drops the locks, at which point nobody (except - * transient RCU lookups) can reach this dentry. - */ - d_free(dentry); - return parent; -} - /** * d_drop - drop a dentry * @dentry: dentry to drop @@ -546,7 +495,30 @@ relock: dentry_lru_del(dentry); /* if it was on the hash then remove it */ __d_drop(dentry); - return d_kill(dentry, parent); + list_del(&dentry->d_u.d_child); + /* + * Inform d_walk() that we are no longer attached to the + * dentry tree + */ + dentry->d_flags |= DCACHE_DENTRY_KILLED; + if (parent) + spin_unlock(&parent->d_lock); + dentry_iput(dentry); + /* + * dentry_iput drops the locks, at which point nobody (except + * transient RCU lookups) can reach this dentry. + */ + BUG_ON((int)dentry->d_lockref.count > 0); + this_cpu_dec(nr_dentry); + if (dentry->d_op && dentry->d_op->d_release) + dentry->d_op->d_release(dentry); + + /* if dentry was never visible to RCU, immediate free is OK */ + if (!(dentry->d_flags & DCACHE_RCUACCESS)) + __d_free(&dentry->d_u.d_rcu); + else + call_rcu(&dentry->d_u.d_rcu, __d_free); + return parent; } /* -- cgit v1.2.3-58-ga151 From 5c47e6d0ad608987b91affbcf7d1fc12dfbe8fb4 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Tue, 29 Apr 2014 16:13:18 -0400 Subject: fold try_prune_one_dentry() Signed-off-by: Al Viro --- fs/dcache.c | 75 +++++++++++++++++++++---------------------------------------- 1 file changed, 25 insertions(+), 50 deletions(-) (limited to 'fs') diff --git a/fs/dcache.c b/fs/dcache.c index 9b15c5c37277..a5540d491954 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -787,47 +787,9 @@ restart: } EXPORT_SYMBOL(d_prune_aliases); -/* - * Try to throw away a dentry - free the inode, dput the parent. - * Requires dentry->d_lock is held, and dentry->d_count == 0. - * Releases dentry->d_lock. - * - * This may fail if locks cannot be acquired no problem, just try again. - */ -static struct dentry * try_prune_one_dentry(struct dentry *dentry) - __releases(dentry->d_lock) -{ - struct dentry *parent; - - parent = dentry_kill(dentry, 0); - /* - * If dentry_kill returns NULL, we have nothing more to do. - * if it returns the same dentry, trylocks failed. In either - * case, just loop again. - * - * Otherwise, we need to prune ancestors too. This is necessary - * to prevent quadratic behavior of shrink_dcache_parent(), but - * is also expected to be beneficial in reducing dentry cache - * fragmentation. - */ - if (!parent) - return NULL; - if (parent == dentry) - return dentry; - - /* Prune ancestors. */ - dentry = parent; - while (dentry) { - if (lockref_put_or_lock(&dentry->d_lockref)) - return NULL; - dentry = dentry_kill(dentry, 1); - } - return NULL; -} - static void shrink_dentry_list(struct list_head *list) { - struct dentry *dentry; + struct dentry *dentry, *parent; rcu_read_lock(); for (;;) { @@ -863,22 +825,35 @@ static void shrink_dentry_list(struct list_head *list) } rcu_read_unlock(); + parent = dentry_kill(dentry, 0); /* - * If 'try_to_prune()' returns a dentry, it will - * be the same one we passed in, and d_lock will - * have been held the whole time, so it will not - * have been added to any other lists. We failed - * to get the inode lock. - * - * We just add it back to the shrink list. + * If dentry_kill returns NULL, we have nothing more to do. */ - dentry = try_prune_one_dentry(dentry); - - rcu_read_lock(); - if (dentry) { + if (!parent) { + rcu_read_lock(); + continue; + } + if (unlikely(parent == dentry)) { + /* + * trylocks have failed and d_lock has been held the + * whole time, so it could not have been added to any + * other lists. Just add it back to the shrink list. + */ + rcu_read_lock(); d_shrink_add(dentry, list); spin_unlock(&dentry->d_lock); + continue; } + /* + * We need to prune ancestors too. This is necessary to prevent + * quadratic behavior of shrink_dcache_parent(), but is also + * expected to be beneficial in reducing dentry cache + * fragmentation. + */ + dentry = parent; + while (dentry && !lockref_put_or_lock(&dentry->d_lockref)) + dentry = dentry_kill(dentry, 1); + rcu_read_lock(); } rcu_read_unlock(); } -- cgit v1.2.3-58-ga151 From b4f0354e968f5fabd39bc85b99fedae4a97589fe Mon Sep 17 00:00:00 2001 From: Al Viro Date: Tue, 29 Apr 2014 23:40:14 -0400 Subject: new helper: dentry_free() The part of old d_free() that dealt with actual freeing of dentry. Taken out of dentry_kill() into a separate function. Signed-off-by: Al Viro --- fs/dcache.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) (limited to 'fs') diff --git a/fs/dcache.c b/fs/dcache.c index a5540d491954..dab7db10d685 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -246,6 +246,15 @@ static void __d_free(struct rcu_head *head) kmem_cache_free(dentry_cache, dentry); } +static void dentry_free(struct dentry *dentry) +{ + /* if dentry was never visible to RCU, immediate free is OK */ + if (!(dentry->d_flags & DCACHE_RCUACCESS)) + __d_free(&dentry->d_u.d_rcu); + else + call_rcu(&dentry->d_u.d_rcu, __d_free); +} + /** * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups * @dentry: the target dentry @@ -513,11 +522,7 @@ relock: if (dentry->d_op && dentry->d_op->d_release) dentry->d_op->d_release(dentry); - /* if dentry was never visible to RCU, immediate free is OK */ - if (!(dentry->d_flags & DCACHE_RCUACCESS)) - __d_free(&dentry->d_u.d_rcu); - else - call_rcu(&dentry->d_u.d_rcu, __d_free); + dentry_free(dentry); return parent; } -- cgit v1.2.3-58-ga151 From 01b6035190b024240a43ac1d8e9c6f964f5f1c63 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Tue, 29 Apr 2014 23:42:52 -0400 Subject: expand the call of dentry_lru_del() in dentry_kill() Signed-off-by: Al Viro --- fs/dcache.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'fs') diff --git a/fs/dcache.c b/fs/dcache.c index dab7db10d685..e482775343a0 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -501,7 +501,12 @@ relock: if ((dentry->d_flags & DCACHE_OP_PRUNE) && !d_unhashed(dentry)) dentry->d_op->d_prune(dentry); - dentry_lru_del(dentry); + if (dentry->d_flags & DCACHE_LRU_LIST) { + if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) + d_lru_del(dentry); + else + d_shrink_del(dentry); + } /* if it was on the hash then remove it */ __d_drop(dentry); list_del(&dentry->d_u.d_child); -- cgit v1.2.3-58-ga151 From 41edf278fc2f042f4e22a12ed87d19c5201210e1 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Thu, 1 May 2014 10:30:00 -0400 Subject: dentry_kill(): don't try to remove from shrink list If the victim in on the shrink list, don't remove it from there. If shrink_dentry_list() manages to remove it from the list before we are done - fine, we'll just free it as usual. If not - mark it with new flag (DCACHE_MAY_FREE) and leave it there. Eventually, shrink_dentry_list() will get to it, remove the sucker from shrink list and call dentry_kill(dentry, 0). Which is where we'll deal with freeing. Since now dentry_kill(dentry, 0) may happen after or during dentry_kill(dentry, 1), we need to recognize that (by seeing DCACHE_DENTRY_KILLED already set), unlock everything and either free the sucker (in case DCACHE_MAY_FREE has been set) or leave it for ongoing dentry_kill(dentry, 1) to deal with. Signed-off-by: Al Viro --- fs/dcache.c | 27 +++++++++++++++++++-------- include/linux/dcache.h | 2 ++ 2 files changed, 21 insertions(+), 8 deletions(-) (limited to 'fs') diff --git a/fs/dcache.c b/fs/dcache.c index e482775343a0..58e26bee7ef4 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -468,7 +468,14 @@ dentry_kill(struct dentry *dentry, int unlock_on_failure) __releases(dentry->d_lock) { struct inode *inode; - struct dentry *parent; + struct dentry *parent = NULL; + bool can_free = true; + + if (unlikely(dentry->d_flags & DCACHE_DENTRY_KILLED)) { + can_free = dentry->d_flags & DCACHE_MAY_FREE; + spin_unlock(&dentry->d_lock); + goto out; + } inode = dentry->d_inode; if (inode && !spin_trylock(&inode->i_lock)) { @@ -479,9 +486,7 @@ relock: } return dentry; /* try again with same dentry */ } - if (IS_ROOT(dentry)) - parent = NULL; - else + if (!IS_ROOT(dentry)) parent = dentry->d_parent; if (parent && !spin_trylock(&parent->d_lock)) { if (inode) @@ -504,8 +509,6 @@ relock: if (dentry->d_flags & DCACHE_LRU_LIST) { if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) d_lru_del(dentry); - else - d_shrink_del(dentry); } /* if it was on the hash then remove it */ __d_drop(dentry); @@ -527,7 +530,15 @@ relock: if (dentry->d_op && dentry->d_op->d_release) dentry->d_op->d_release(dentry); - dentry_free(dentry); + spin_lock(&dentry->d_lock); + if (dentry->d_flags & DCACHE_SHRINK_LIST) { + dentry->d_flags |= DCACHE_MAY_FREE; + can_free = false; + } + spin_unlock(&dentry->d_lock); +out: + if (likely(can_free)) + dentry_free(dentry); return parent; } @@ -829,7 +840,7 @@ static void shrink_dentry_list(struct list_head *list) * We found an inuse dentry which was not removed from * the LRU because of laziness during lookup. Do not free it. */ - if (dentry->d_lockref.count) { + if ((int)dentry->d_lockref.count > 0) { spin_unlock(&dentry->d_lock); continue; } diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 3b9bfdb83ba6..3c7ec327ebd2 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -221,6 +221,8 @@ struct dentry_operations { #define DCACHE_SYMLINK_TYPE 0x00300000 /* Symlink */ #define DCACHE_FILE_TYPE 0x00400000 /* Other file type */ +#define DCACHE_MAY_FREE 0x00800000 + extern seqlock_t rename_lock; static inline int dname_external(const struct dentry *dentry) -- cgit v1.2.3-58-ga151 From fe91522a7ba82ca1a51b07e19954b3825e4aaa22 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 3 May 2014 00:02:25 -0400 Subject: don't remove from shrink list in select_collect() If we find something already on a shrink list, just increment data->found and do nothing else. Loops in shrink_dcache_parent() and check_submounts_and_drop() will do the right thing - everything we did put into our list will be evicted and if there had been nothing, but data->found got non-zero, well, we have somebody else shrinking those guys; just try again. Signed-off-by: Al Viro --- fs/dcache.c | 31 ++++++++++--------------------- 1 file changed, 10 insertions(+), 21 deletions(-) (limited to 'fs') diff --git a/fs/dcache.c b/fs/dcache.c index 58e26bee7ef4..f39a6f5a1220 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1229,34 +1229,23 @@ static enum d_walk_ret select_collect(void *_data, struct dentry *dentry) if (data->start == dentry) goto out; - /* - * move only zero ref count dentries to the dispose list. - * - * Those which are presently on the shrink list, being processed - * by shrink_dentry_list(), shouldn't be moved. Otherwise the - * loop in shrink_dcache_parent() might not make any progress - * and loop forever. - */ - if (dentry->d_lockref.count) { - dentry_lru_del(dentry); - } else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) { - /* - * We can't use d_lru_shrink_move() because we - * need to get the global LRU lock and do the - * LRU accounting. - */ - d_lru_del(dentry); - d_shrink_add(dentry, &data->dispose); + if (dentry->d_flags & DCACHE_SHRINK_LIST) { data->found++; - ret = D_WALK_NORETRY; + } else { + if (dentry->d_flags & DCACHE_LRU_LIST) + d_lru_del(dentry); + if (!dentry->d_lockref.count) { + d_shrink_add(dentry, &data->dispose); + data->found++; + } } /* * We can return to the caller if we have found some (this * ensures forward progress). We'll be coming back to find * the rest. */ - if (data->found && need_resched()) - ret = D_WALK_QUIT; + if (!list_empty(&data->dispose)) + ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY; out: return ret; } -- cgit v1.2.3-58-ga151 From 9c8c10e262e0f62cb2530f1b076de979123183dd Mon Sep 17 00:00:00 2001 From: Al Viro Date: Fri, 2 May 2014 20:36:10 -0400 Subject: more graceful recovery in umount_collect() Start with shrink_dcache_parent(), then scan what remains. First of all, BUG() is very much an overkill here; we are holding ->s_umount, and hitting BUG() means that a lot of interesting stuff will be hanging after that point (sync(2), for example). Moreover, in cases when there had been more than one leak, we'll be better off reporting all of them. And more than just the last component of pathname - %pd is there for just such uses... That was the last user of dentry_lru_del(), so kill it off... Signed-off-by: Al Viro --- fs/dcache.c | 101 +++++++++++++++--------------------------------------------- 1 file changed, 25 insertions(+), 76 deletions(-) (limited to 'fs') diff --git a/fs/dcache.c b/fs/dcache.c index f39a6f5a1220..2321e1a861f6 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -395,22 +395,6 @@ static void dentry_lru_add(struct dentry *dentry) d_lru_add(dentry); } -/* - * Remove a dentry with references from the LRU. - * - * If we are on the shrink list, then we can get to try_prune_one_dentry() and - * lose our last reference through the parent walk. In this case, we need to - * remove ourselves from the shrink list, not the LRU. - */ -static void dentry_lru_del(struct dentry *dentry) -{ - if (dentry->d_flags & DCACHE_LRU_LIST) { - if (dentry->d_flags & DCACHE_SHRINK_LIST) - return d_shrink_del(dentry); - d_lru_del(dentry); - } -} - /** * d_drop - drop a dentry * @dentry: dentry to drop @@ -1275,45 +1259,35 @@ void shrink_dcache_parent(struct dentry *parent) } EXPORT_SYMBOL(shrink_dcache_parent); -static enum d_walk_ret umount_collect(void *_data, struct dentry *dentry) +static enum d_walk_ret umount_check(void *_data, struct dentry *dentry) { - struct select_data *data = _data; - enum d_walk_ret ret = D_WALK_CONTINUE; + /* it has busy descendents; complain about those instead */ + if (!list_empty(&dentry->d_subdirs)) + return D_WALK_CONTINUE; - if (dentry->d_lockref.count) { - dentry_lru_del(dentry); - if (likely(!list_empty(&dentry->d_subdirs))) - goto out; - if (dentry == data->start && dentry->d_lockref.count == 1) - goto out; - printk(KERN_ERR - "BUG: Dentry %p{i=%lx,n=%s}" - " still in use (%d)" - " [unmount of %s %s]\n", + /* root with refcount 1 is fine */ + if (dentry == _data && dentry->d_lockref.count == 1) + return D_WALK_CONTINUE; + + printk(KERN_ERR "BUG: Dentry %p{i=%lx,n=%pd} " + " still in use (%d) [unmount of %s %s]\n", dentry, dentry->d_inode ? dentry->d_inode->i_ino : 0UL, - dentry->d_name.name, + dentry, dentry->d_lockref.count, dentry->d_sb->s_type->name, dentry->d_sb->s_id); - BUG(); - } else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) { - /* - * We can't use d_lru_shrink_move() because we - * need to get the global LRU lock and do the - * LRU accounting. - */ - if (dentry->d_flags & DCACHE_LRU_LIST) - d_lru_del(dentry); - d_shrink_add(dentry, &data->dispose); - data->found++; - ret = D_WALK_NORETRY; - } -out: - if (data->found && need_resched()) - ret = D_WALK_QUIT; - return ret; + WARN_ON(1); + return D_WALK_CONTINUE; +} + +static void do_one_tree(struct dentry *dentry) +{ + shrink_dcache_parent(dentry); + d_walk(dentry, dentry, umount_check, NULL); + d_drop(dentry); + dput(dentry); } /* @@ -1323,40 +1297,15 @@ void shrink_dcache_for_umount(struct super_block *sb) { struct dentry *dentry; - if (down_read_trylock(&sb->s_umount)) - BUG(); + WARN(down_read_trylock(&sb->s_umount), "s_umount should've been locked"); dentry = sb->s_root; sb->s_root = NULL; - for (;;) { - struct select_data data; - - INIT_LIST_HEAD(&data.dispose); - data.start = dentry; - data.found = 0; - - d_walk(dentry, &data, umount_collect, NULL); - if (!data.found) - break; - - shrink_dentry_list(&data.dispose); - cond_resched(); - } - d_drop(dentry); - dput(dentry); + do_one_tree(dentry); while (!hlist_bl_empty(&sb->s_anon)) { - struct select_data data; - dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash); - - INIT_LIST_HEAD(&data.dispose); - data.start = NULL; - data.found = 0; - - d_walk(dentry, &data, umount_collect, NULL); - if (data.found) - shrink_dentry_list(&data.dispose); - cond_resched(); + dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash)); + do_one_tree(dentry); } } -- cgit v1.2.3-58-ga151 From 60942f2f235ce7b817166cdf355eed729094834d Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Fri, 2 May 2014 15:38:39 -0400 Subject: dcache: don't need rcu in shrink_dentry_list() Since now the shrink list is private and nobody can free the dentry while it is on the shrink list, we can remove RCU protection from this. Signed-off-by: Miklos Szeredi Signed-off-by: Al Viro --- fs/dcache.c | 27 ++++----------------------- 1 file changed, 4 insertions(+), 23 deletions(-) (limited to 'fs') diff --git a/fs/dcache.c b/fs/dcache.c index 2321e1a861f6..42ae01eefc07 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -796,23 +796,9 @@ static void shrink_dentry_list(struct list_head *list) { struct dentry *dentry, *parent; - rcu_read_lock(); - for (;;) { - dentry = list_entry_rcu(list->prev, struct dentry, d_lru); - if (&dentry->d_lru == list) - break; /* empty */ - - /* - * Get the dentry lock, and re-verify that the dentry is - * this on the shrinking list. If it is, we know that - * DCACHE_SHRINK_LIST and DCACHE_LRU_LIST are set. - */ + while (!list_empty(list)) { + dentry = list_entry(list->prev, struct dentry, d_lru); spin_lock(&dentry->d_lock); - if (dentry != list_entry(list->prev, struct dentry, d_lru)) { - spin_unlock(&dentry->d_lock); - continue; - } - /* * The dispose list is isolated and dentries are not accounted * to the LRU here, so we can simply remove it from the list @@ -828,23 +814,20 @@ static void shrink_dentry_list(struct list_head *list) spin_unlock(&dentry->d_lock); continue; } - rcu_read_unlock(); parent = dentry_kill(dentry, 0); /* * If dentry_kill returns NULL, we have nothing more to do. */ - if (!parent) { - rcu_read_lock(); + if (!parent) continue; - } + if (unlikely(parent == dentry)) { /* * trylocks have failed and d_lock has been held the * whole time, so it could not have been added to any * other lists. Just add it back to the shrink list. */ - rcu_read_lock(); d_shrink_add(dentry, list); spin_unlock(&dentry->d_lock); continue; @@ -858,9 +841,7 @@ static void shrink_dentry_list(struct list_head *list) dentry = parent; while (dentry && !lockref_put_or_lock(&dentry->d_lockref)) dentry = dentry_kill(dentry, 1); - rcu_read_lock(); } - rcu_read_unlock(); } static enum lru_status -- cgit v1.2.3-58-ga151 From 50c6e282bdf5e8dabf8d7cf7b162545a55645fd9 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Sun, 4 May 2014 13:03:32 +0200 Subject: posix_acl: handle NULL ACL in posix_acl_equiv_mode Various filesystems don't bother checking for a NULL ACL in posix_acl_equiv_mode, and thus can dereference a NULL pointer when it gets passed one. This usually happens from the NFS server, as the ACL tools never pass a NULL ACL, but instead of one representing the mode bits. Instead of adding boilerplat to all filesystems put this check into one place, which will allow us to remove the check from other filesystems as well later on. Signed-off-by: Christoph Hellwig Reported-by: Ben Greear Reported-by: Marco Munderloh , Cc: Chuck Lever Cc: stable@vger.kernel.org Signed-off-by: Al Viro --- fs/posix_acl.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'fs') diff --git a/fs/posix_acl.c b/fs/posix_acl.c index 9e363e41dacc..0855f772cd41 100644 --- a/fs/posix_acl.c +++ b/fs/posix_acl.c @@ -246,6 +246,12 @@ posix_acl_equiv_mode(const struct posix_acl *acl, umode_t *mode_p) umode_t mode = 0; int not_equiv = 0; + /* + * A null ACL can always be presented as mode bits. + */ + if (!acl) + return 0; + FOREACH_ACL_ENTRY(pa, acl, pe) { switch (pa->e_tag) { case ACL_USER_OBJ: -- cgit v1.2.3-58-ga151