From a280df32db291f41b3922ac218674be526af5b9b Mon Sep 17 00:00:00 2001 From: "J. Bruce Fields" Date: Thu, 19 Jul 2007 01:49:18 -0700 Subject: [PATCH] nfsd: fix possible read-ahead cache and export table corruption The value of nperbucket calculated here is too small--we should be rounding up instead of down--with the result that the index j in the following loop can overflow the raparm_hash array. At least in my case, the next thing in memory turns out to be export_table, so the symptoms I see are crashes caused by the appearance of four zeroed-out export entries in the first bucket of the hash table of exports (which were actually entries in the readahead cache, a pointer to which had been written to the export table in this initialization code). It looks like the bug was probably introduced with commit fce1456a19f5c08b688c29f00ef90fdfa074c79b ("knfsd: make the readahead params cache SMP-friendly"). Cc: Cc: Greg Banks Signed-off-by: "J. Bruce Fields" Acked-by: NeilBrown Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/nfsd/vfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index e90f4a8a1d01..b8da5ddb3a0a 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -1916,7 +1916,7 @@ nfsd_racache_init(int cache_size) raparm_hash[i].pb_head = NULL; spin_lock_init(&raparm_hash[i].pb_lock); } - nperbucket = cache_size >> RAPARM_HASH_BITS; + nperbucket = DIV_ROUND_UP(cache_size, RAPARM_HASH_SIZE); for (i = 0; i < cache_size - 1; i++) { if (i % nperbucket == 0) raparm_hash[j++].pb_head = raparml + i; -- 2.30.2