[patch 16/20] Fix ipv4 routing locking bug

Greg KH
2006-08-21T18:49:40Z

[-- Attachment #1: fix-ipv4-routing-locking-bug.patch --]
[-- Type: text/plain, Size: 2499 bytes --]

-stable review patch. If anyone has any objections, please let us know.

------------------

From: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>

[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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
net/ipv4/fib_semantics.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

--- linux-2.6.17.9.orig/net/ipv4/fib_semantics.c
+++ linux-2.6.17.9/net/ipv4/fib_semantics.c
@@ -160,7 +160,7 @@ 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)
@@ -173,7 +173,7 @@ void fib_release_info(struct fib_info *f
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)
@@ -599,7 +599,7 @@ static void fib_hash_move(struct hlist_h
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;
@@ -640,7 +640,7 @@ static void fib_hash_move(struct hlist_h
}
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);
@@ -822,7 +822,7 @@ 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) {
@@ -841,7 +841,7 @@ 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:

--