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Test your applicationsThere is no fixed version for RHEL:9 kernel-64k-debug-modules-partner.
Note: Versions mentioned in the description apply only to the upstream kernel-64k-debug-modules-partner package and not the kernel-64k-debug-modules-partner package as distributed by RHEL.
See How to fix? for RHEL:9 relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
fs/notify: call exportfs_encode_fid with s_umount
Calling intotify_show_fdinfo() on fd watching an overlayfs inode, while the overlayfs is being unmounted, can lead to dereferencing NULL ptr.
This issue was found by syzkaller.
Race Condition Diagram:
Thread 1 Thread 2
generic_shutdown_super() shrink_dcache_for_umount sb->s_root = NULL
|
| vfs_read()
| inotify_fdinfo()
| * inode get from mark *
| show_mark_fhandle(m, inode)
| exportfs_encode_fid(inode, ..)
| ovl_encode_fh(inode, ..)
| ovl_check_encode_origin(inode)
| * deref i_sb->s_root *
|
|
v
fsnotify_sb_delete(sb)
Which then leads to:
[ 32.133461] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000006: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI [ 32.134438] KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037] [ 32.135032] CPU: 1 UID: 0 PID: 4468 Comm: systemd-coredum Not tainted 6.17.0-rc6 #22 PREEMPT(none)
<snip registers, unreliable trace>
[ 32.143353] Call Trace: [ 32.143732] ovl_encode_fh+0xd5/0x170 [ 32.144031] exportfs_encode_inode_fh+0x12f/0x300 [ 32.144425] show_mark_fhandle+0xbe/0x1f0 [ 32.145805] inotify_fdinfo+0x226/0x2d0 [ 32.146442] inotify_show_fdinfo+0x1c5/0x350 [ 32.147168] seq_show+0x530/0x6f0 [ 32.147449] seq_read_iter+0x503/0x12a0 [ 32.148419] seq_read+0x31f/0x410 [ 32.150714] vfs_read+0x1f0/0x9e0 [ 32.152297] ksys_read+0x125/0x240
IOW ovl_check_encode_origin derefs inode->i_sb->s_root, after it was set to NULL in the unmount path.
Fix it by protecting calling exportfs_encode_fid() from show_mark_fhandle() with s_umount lock.
This form of fix was suggested by Amir in 1.