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[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>
This commit is contained in:
Alexey Kuznetsov 2006-08-17 16:44:46 -07:00 committed by David S. Miller
parent acd6e00b8e
commit 6e8fcbf640
1 changed files with 6 additions and 6 deletions
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12
net/ipv4/fib_semantics.c
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@ -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: