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authorOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>2006-06-22 14:47:21 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-22 15:05:57 -0700
commit09d967c6f32b35eab15b45862ae16e4f06259d8e (patch)
tree9fca9dda390612041f857a33cb746fe1eb28b60a /fs/exec.c
parent0e5b3781591cc954037c08ef78edf7f1192d38c5 (diff)
[PATCH] Fix a race condition between ->i_mapping and iput()
This race became a cause of oops, and can reproduce by the following. while true; do dd if=/dev/zero of=/dev/.static/dev/hdg1 bs=512 count=1000 & sync done This race condition was between __sync_single_inode() and iput(). cpu0 (fs's inode) cpu1 (bdev's inode) ----------------- ------------------- close("/dev/hda2") [...] __sync_single_inode() /* copy the bdev's ->i_mapping */ mapping = inode->i_mapping; generic_forget_inode() bdev_clear_inode() /* restre the fs's ->i_mapping */ inode->i_mapping = &inode->i_data; /* bdev's inode was freed */ destroy_inode(inode); if (wait) { /* dereference a freed bdev's mapping->host */ filemap_fdatawait(mapping); /* Oops */ Since __sync_single_inode() is only taking a ref-count of fs's inode, the another process can be close() and freeing the bdev's inode while writing fs's inode. So, __sync_signle_inode() accesses the freed ->i_mapping, oops. This patch takes a ref-count on the bdev's inode for the fs's inode before setting a ->i_mapping, and the clear_inode() of the fs's inode does iput() on the bdev's inode. So if the fs's inode is still living, bdev's inode shouldn't be freed. Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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