Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: - [High] Lockless read of daxdev->valid lacks a read memory barrier, leading to a TOCTOU race that can yield a NULL pointer and a zero error code. --
commit 592a1b20aa272f01a78424966dd5d63af6c63cf8 Author: John Groves <[email protected]> famfs: Register secondary daxdevs by path (FAMFSIOC_DAXDEV_OPEN) Famfs file maps (fmaps) may reference multiple daxdevs. Before passing an fmap that references a new daxdev, the daxdev is pushed into the kernel via FAMFSIOC_DAXDEV_OPEN). This adds daxdevs to daxdev_table for index-based resolution from famfs extents to daxdevs. > kernel via FAMFSIOC_DAXDEV_OPEN). This adds daxdevs to daxdev_table for This isn't a bug, but there is an unmatched closing parenthesis after FAMFSIOC_DAXDEV_OPEN. > diff --git a/fs/famfs/famfs_file.c b/fs/famfs/famfs_file.c > index 2200f168aa79d..eba80dab0562d 100644 > --- a/fs/famfs/famfs_file.c > +++ b/fs/famfs/famfs_file.c [ ... ] > +static int > +famfs_daxdev_open(struct file *file, void __user *arg) > +{ [ ... ] > + /* > + * The daxdev table is allocated at mount time (for the slot-0 primary), > + * so it is always present here; no need to allocate it. > + */ > + rc = famfs_install_daxdev(fsi, sb, dd.daxdev_index, devno, path); [Severity: High] Does exposing famfs_install_daxdev() to concurrent execution via this ioctl trigger a race condition in the lockless readers? famfs_install_daxdev() uses wmb() to ensure daxdev->devp is visible before setting daxdev->valid = 1: fs/famfs/famfs_inode.c:famfs_install_daxdev() { ... wmb(); /* All other fields must be visible before valid */ daxdev->valid = 1; ... } However, the readers famfs_dax_err() and famfs_daxdev_from_index() lack a pairing smp_rmb(): fs/famfs/famfs_file.c:famfs_dax_err() { if (!dd->valid) { pr_debug("%s: daxdev=%s invalid\n", __func__, dd->name); return -EIO; } ... } fs/famfs/famfs_file.c:famfs_daxdev_from_index() { ... rc = famfs_dax_err(dd); if (rc) { *errp = rc; return NULL; } *errp = 0; return dd->devp; } Could the CPU or compiler reorder the loads, reading a stale NULL for devp before reading valid == 1, resulting in famfs_daxdev_from_index() returning NULL with a success error code (0)? -- Sashiko AI review ยท https://sashiko.dev/#/patchset/010001a04e801a4e-8eb212cd-b263-4043-ab65-33e480d2d7d4-000...@email.amazonses.com?part=9
