[PATCH] f2fs: fix potential .flags overflow on 32bit architecture

[Chao Yu]

From: Chao Yu <yuchao0@xxxxxxxxxx>

f2fs_inode_info.flags is unsigned long variable, it has 32 bits
in 32bit architecture, since we introduced FI_MMAP_FILE flag
when we support data compression, we may access memory cross
the border of .flags field, corrupting .i_sem field, result in
below deadlock.

To fix this issue, let's introduce .extra_flags to grab extra
space to store those new flags.

Call Trace:
 __schedule+0x8d0/0x13fc
 ? mark_held_locks+0xac/0x100
 schedule+0xcc/0x260
 rwsem_down_write_slowpath+0x3ab/0x65d
 down_write+0xc7/0xe0
 f2fs_drop_nlink+0x3d/0x600 [f2fs]
 f2fs_delete_inline_entry+0x300/0x440 [f2fs]
 f2fs_delete_entry+0x3a1/0x7f0 [f2fs]
 f2fs_unlink+0x500/0x790 [f2fs]
 vfs_unlink+0x211/0x490
 do_unlinkat+0x483/0x520
 sys_unlink+0x4a/0x70
 do_fast_syscall_32+0x12b/0x683
 entry_SYSENTER_32+0xaa/0x102

Fixes: 4c8ff7095bef ("f2fs: support data compression")
Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
---
 fs/f2fs/f2fs.h  | 26 ++++++++++++++++++++------
 fs/f2fs/inode.c |  1 +
 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index fcafa68212eb..fcd22df2e9ca 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -695,6 +695,7 @@ struct f2fs_inode_info {
 
 	/* Use below internally in f2fs*/
 	unsigned long flags;		/* use to pass per-file flags */
+	unsigned long extra_flags;	/* extra flags */
 	struct rw_semaphore i_sem;	/* protect fi info */
 	atomic_t dirty_pages;		/* # of dirty pages */
 	f2fs_hash_t chash;		/* hash value of given file name */
@@ -2569,7 +2570,7 @@ enum {
 };
 
 static inline void __mark_inode_dirty_flag(struct inode *inode,
-						int flag, bool set)
+					unsigned long long flag, bool set)
 {
 	switch (flag) {
 	case FI_INLINE_XATTR:
@@ -2588,20 +2589,33 @@ static inline void __mark_inode_dirty_flag(struct inode *inode,
 
 static inline void set_inode_flag(struct inode *inode, int flag)
 {
-	if (!test_bit(flag, &F2FS_I(inode)->flags))
-		set_bit(flag, &F2FS_I(inode)->flags);
+	if ((1 << flag) <= sizeof(unsigned long)) {
+		if (!test_bit(flag, &F2FS_I(inode)->flags))
+			set_bit(flag, &F2FS_I(inode)->flags);
+	} else {
+		if (!test_bit(flag - 32, &F2FS_I(inode)->extra_flags))
+			set_bit(flag - 32, &F2FS_I(inode)->extra_flags);
+	}
 	__mark_inode_dirty_flag(inode, flag, true);
 }
 
 static inline int is_inode_flag_set(struct inode *inode, int flag)
 {
-	return test_bit(flag, &F2FS_I(inode)->flags);
+	if ((1 << flag) <= sizeof(unsigned long))
+		return test_bit(flag, &F2FS_I(inode)->flags);
+	else
+		return test_bit(flag - 32, &F2FS_I(inode)->extra_flags);
 }
 
 static inline void clear_inode_flag(struct inode *inode, int flag)
 {
-	if (test_bit(flag, &F2FS_I(inode)->flags))
-		clear_bit(flag, &F2FS_I(inode)->flags);
+	if ((1 << flag) <= sizeof(unsigned long)) {
+		if (test_bit(flag, &F2FS_I(inode)->flags))
+			clear_bit(flag, &F2FS_I(inode)->flags);
+	} else {
+		if (test_bit(flag - 32, &F2FS_I(inode)->extra_flags))
+			clear_bit(flag - 32, &F2FS_I(inode)->extra_flags);
+	}
 	__mark_inode_dirty_flag(inode, flag, false);
 }
 
diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
index 44e08bf2e2b4..ca924d7e0e30 100644
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -363,6 +363,7 @@ static int do_read_inode(struct inode *inode)
 	if (S_ISREG(inode->i_mode))
 		fi->i_flags &= ~F2FS_PROJINHERIT_FL;
 	fi->flags = 0;
+	fi->extra_flags = 0;
 	fi->i_advise = ri->i_advise;
 	fi->i_pino = le32_to_cpu(ri->i_pino);
 	fi->i_dir_level = ri->i_dir_level;
-- 
2.22.0