Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
ext4: fix timer use-after-free on failed mount
Syzbot has found an ODEBUG bug in ext4_fill_super
The del_timer_sync function cancels the s_err_report timer, which reminds about filesystem errors daily. We should guarantee the timer is no longer active before kfree(sbi).
When filesystem mounting fails, the flow goes to failed_mount3, where an error occurs when ext4_stop_mmpd is called, causing a read I/O failure. This triggers the ext4_handle_error function that ultimately re-arms the timer, leaving the s_err_report timer active before kfree(sbi) is called.
Fix the issue by canceling the s_err_report timer after calling ext4_stop_mmpd.
Details
- Affected product:
- AlmaLinux 9.2 ESU , CentOS 6 ELS , CentOS 7 ELS , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , CloudLinux 6 ELS , CloudLinux 7 ELS , Oracle Linux 6 ELS , Oracle Linux 7 ELS , RHEL 7 ELS , Ubuntu 16.04 ELS , Ubuntu 18.04 ELS
- Affected packages:
- kernel @ 4.18.0 (+15 more)
In the Linux kernel, the following vulnerability has been resolved:
ext4: fix timer use-after-free on failed mount
Syzbot has found an ODEBUG bug in ext4_fill_super
The del_timer_sync function cancels the s_err_report timer, which reminds about filesystem errors daily. We should guarantee the timer is no longer active before kfree(sbi).
When filesystem mounting fails, the flow goes to failed_mount3, where an error occurs when ext4_stop_mmpd is called, causing a read I/O failure. This triggers the ext4_handle_error function that ultimately re-arms the timer, leaving the s_err_report timer active before kfree(sbi) is called.
Fix the issue by canceling the s_err_report timer after calling ext4_stop_mmpd.