Commit a68e61e8 authored Feb 04, 2009 by Tony Battersby Committed by Linus Torvalds Feb 05, 2009

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 <tonyb@cybernetics.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Reported-by: Jiri Olsa <olsajiri@gmail.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: <stable@kernel.org>		[2.6.everything]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 1f5e31d7

ipc/shm.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -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++;

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