[IPV4]: severe locking bug in fib_semantics.c

Found in 2.4 by Yixin Pan <yxpan@hotmail.com>.

> When I read fib_semantics.c of Linux-2.4.32, write_lock(&fib_info_lock) =
> is used in fib_release_info() instead of write_lock_bh(&fib_info_lock).  =
> Is the following case possible: a BH interrupts fib_release_info() while =
> holding the write lock, and calls ip_check_fib_default() which calls =
> read_lock(&fib_info_lock), and spin forever.

Signed-off-by: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 6 deletions

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 9be53a8e72c3..51738000f3dc 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -159,7 +159,7 @@ void free_fib_info(struct fib_info *fi)
 
 void fib_release_info(struct fib_info *fi)
 {
-        write_lock(&fib_info_lock);
+        write_lock_bh(&fib_info_lock);
         if (fi && --fi->fib_treeref == 0) {
                 hlist_del(&fi->fib_hash);
                 if (fi->fib_prefsrc)
@@ -172,7 +172,7 @@ void fib_release_info(struct fib_info *fi)
                 fi->fib_dead = 1;
                 fib_info_put(fi);
         }
-        write_unlock(&fib_info_lock);
+        write_unlock_bh(&fib_info_lock);
 }
 
 static __inline__ int nh_comp(const struct fib_info *fi, const struct fib_info *ofi)
@@ -598,7 +598,7 @@ static void fib_hash_move(struct hlist_head *new_info_hash,
         unsigned int old_size = fib_hash_size;
         unsigned int i, bytes;
 
-        write_lock(&fib_info_lock);
+        write_lock_bh(&fib_info_lock);
         old_info_hash = fib_info_hash;
         old_laddrhash = fib_info_laddrhash;
         fib_hash_size = new_size;
@@ -639,7 +639,7 @@ static void fib_hash_move(struct hlist_head *new_info_hash,
         }
         fib_info_laddrhash = new_laddrhash;
 
-        write_unlock(&fib_info_lock);
+        write_unlock_bh(&fib_info_lock);
 
         bytes = old_size * sizeof(struct hlist_head *);
         fib_hash_free(old_info_hash, bytes);
@@ -820,7 +820,7 @@ link_it:
 
         fi->fib_treeref++;
         atomic_inc(&fi->fib_clntref);
-        write_lock(&fib_info_lock);
+        write_lock_bh(&fib_info_lock);
         hlist_add_head(&fi->fib_hash,
                        &fib_info_hash[fib_info_hashfn(fi)]);
         if (fi->fib_prefsrc) {
@@ -839,7 +839,7 @@ link_it:
                 head = &fib_info_devhash[hash];
                 hlist_add_head(&nh->nh_hash, head);
         } endfor_nexthops(fi)
-        write_unlock(&fib_info_lock);
+        write_unlock_bh(&fib_info_lock);
         return fi;
 
 err_inval: