ext4 super.c fix: Replace SB_RDONLY with EXT4_FLAGS_SHUTDOWN to prevent filesystem freeze

From this webpage screenshot, we can extract the following key information about the vulnerability: 1. Vulnerability Description: - Issue: When a filesystem is mounted in read-only mode (errors=remount-ro), the SB_RDONLY flag is set to prevent all filesystem modifications. This leads to a filesystem freeze. - Cause: The code fails to properly execute the filesystem unmount operation (sb->s_umount) upon encountering an error, instead directly setting the SB_RDONLY flag. - Impact: This causes the filesystem to freeze, as the code becomes confused when setting the SB_RDONLY flag. 2. Fix: - Solution: Before setting the SB_RDONLY flag, set the EXT4_FLAGS_SHUTDOWN flag to ensure all filesystem modifications are blocked. - Result: Setting the SB_RDONLY flag is no longer necessary, as all filesystem modifications are already blocked by setting the EXT4_FLAGS_SHUTDOWN flag. 3. Related Links: - Report Link: https://lore.kernel.org/all/000000000000b90a8e061e21d12f@go - Patch Link: https://patchwork.ink/20240805201241.27286-1-jack@suse.cz 4. Authors and Contributors: - Author: Jan Kara - Submitter: Theodore Ts'o - Reporter: Christian Brauner - Signer: Jan Kara - Reviewer: Christian Brauner - Signer: Theodore Ts'o 5. Code Changes: - File: fs/ext4/super.c - Lines: -735,11 +735,12 - Change Details: In the function, the code that sets the SB_RDONLY flag is replaced with code that sets the EXT4_FLAGS_SHUTDOWN flag. This information indicates that the vulnerability stems from improper error handling when mounting a filesystem in read-only mode. The fix involves setting the EXT4_FLAGS_SHUTDOWN flag to block all filesystem modifications, thereby preventing the filesystem freeze.

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ext4 super.c fix: Replace SB_RDONLY with EXT4_FLAGS_SHUTDOWN to prevent filesystem freeze