ovl: avoid deadlock on directory ioctl
commit b854cc65 upstream. The function ovl_dir_real_file() currently uses the inode lock to serialize writes to the od->upperfile field. However, this function will get called by ovl_ioctl_set_flags(), which utilizes the inode lock too. In this case ovl_dir_real_file() will try to claim a lock that is owned by a function in its call stack, which won't get released before ovl_dir_real_file() returns. Fix by replacing the open coded compare and exchange by an explicit atomic op. Fixes: 61536bed ("ovl: support [S|G]ETFLAGS and FS[S|G]ETXATTR ioctls for directories") Cc: stable@vger.kernel.org # v5.10 Reported-by:Icenowy Zheng <icenowy@aosc.io> Tested-by:
Icenowy Zheng <icenowy@aosc.io> Signed-off-by:
Miklos Szeredi <mszeredi@redhat.com> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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fb8caef7
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