Archive-Team
/
zfs
2
0
Fork 0
Code Issues Pull Requests Packages Projects Releases 103 Wiki Activity

zvols: prevent overflow of minor device numbers 

currently, the linux kernel allows 2^20 minor devices per major device
number.  ZFS reserves blocks of 2^4 minors per zvol: 1 for the zvol
itself, the other 15 for the first partitions of that zvol. as a result,
only 2^16 such blocks are available for use.

there are no checks in place to avoid overflowing into the major device
number when more than 2^16 zvols are allocated (with volmode=dev or
default). instead of ignoring this limit, which comes with all sorts of
weird knock-on effects, detect this situation and simply fail allocating
the zvol block device early on.

without this safeguard, the kernel will reject the attempt to create an
already existing block device, but ZFS doesn't handle this error and
gets confused about which zvol occupies which minor slot, potentially
resulting in kernel NULL derefs and other issues later on.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
Closes #16006
This commit is contained in:
Fabian-Gruenbichler 2024-03-29 22:37:40 +01:00 committed by GitHub
parent b1e46f869e
commit c0aab8b8f9
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
1 changed files with 7 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
module/os/linux/zfs/zvol_os.c
View File

@ -1314,6 +1314,13 @@ zvol_os_create_minor(const char *name)
if (idx < 0)
return (SET_ERROR(-idx));
minor = idx << ZVOL_MINOR_BITS;
if (MINOR(minor) != minor) {
/* too many partitions can cause an overflow */
zfs_dbgmsg("zvol: create minor overflow: %s, minor %u/%u",
name, minor, MINOR(minor));
ida_simple_remove(&zvol_ida, idx);
return (SET_ERROR(EINVAL));
}
zv = zvol_find_by_name_hash(name, hash, RW_NONE);
if (zv) {