From a68e61e8ff2d46327a37b69056998b47745db6fa Mon Sep 17 00:00:00 2001 From: Tony Battersby Date: Wed, 4 Feb 2009 15:12:04 -0800 Subject: [PATCH] shm: fix shmctl(SHM_INFO) lockup with !CONFIG_SHMEM shm_get_stat() assumes that the inode is a "struct shmem_inode_info", which is incorrect for !CONFIG_SHMEM (see fs/ramfs/inode.c: ramfs_get_inode() vs. mm/shmem.c: shmem_get_inode()). This bad assumption can cause shmctl(SHM_INFO) to lockup when shm_get_stat() tries to spin_lock(&info->lock). Users of !CONFIG_SHMEM may encounter this lockup simply by invoking the 'ipcs' command. Reported by Jiri Olsa back in February 2008: http://lkml.org/lkml/2008/2/29/74 Signed-off-by: Tony Battersby Cc: Jiri Kosina Reported-by: Jiri Olsa Cc: Hugh Dickins Cc: [2.6.everything] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- ipc/shm.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/ipc/shm.c b/ipc/shm.c index c0a021f7f41a..f8f69fad3a27 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -565,11 +565,15 @@ static void shm_get_stat(struct ipc_namespace *ns, unsigned long *rss, struct hstate *h = hstate_file(shp->shm_file); *rss += pages_per_huge_page(h) * mapping->nrpages; } else { +#ifdef CONFIG_SHMEM struct shmem_inode_info *info = SHMEM_I(inode); spin_lock(&info->lock); *rss += inode->i_mapping->nrpages; *swp += info->swapped; spin_unlock(&info->lock); +#else + *rss += inode->i_mapping->nrpages; +#endif } total++; -- 2.20.1