'type' is a user-controlled value used to index 'sb_dqopt(sb)->files'. Clamp 'type' to the size of the array to avoid a speculative out-of-bounds read.
These gadgets were found with the help of smatch: * fs/ext4/super.c:5741 ext4_quota_read() warn: potential spectre issue 'sb_dqopt(sb)->files' [r] * fs/ext4/super.c:5778 ext4_quota_write() warn: potential spectre issue 'sb_dqopt(sb)->files' [r] Cc: Josh Poimboeuf <[email protected]> Cc: [email protected] Signed-off-by: Jeremy Cline <[email protected]> --- fs/ext4/super.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index c04a09b51742..de358eba024a 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -5693,10 +5693,13 @@ static int ext4_enable_quotas(struct super_block *sb) static int ext4_quota_off(struct super_block *sb, int type) { - struct inode *inode = sb_dqopt(sb)->files[type]; + struct inode *inode; handle_t *handle; int err; + type = array_index_nospec(type, MAXQUOTAS); + inode = sb_dqopt(sb)->files[type]; + /* Force all delayed allocation blocks to be allocated. * Caller already holds s_umount sem */ if (test_opt(sb, DELALLOC)) @@ -5740,13 +5743,17 @@ static int ext4_quota_off(struct super_block *sb, int type) static ssize_t ext4_quota_read(struct super_block *sb, int type, char *data, size_t len, loff_t off) { - struct inode *inode = sb_dqopt(sb)->files[type]; + struct inode *inode; ext4_lblk_t blk = off >> EXT4_BLOCK_SIZE_BITS(sb); int offset = off & (sb->s_blocksize - 1); int tocopy; size_t toread; struct buffer_head *bh; - loff_t i_size = i_size_read(inode); + loff_t i_size; + + type = array_index_nospec(type, MAXQUOTAS); + inode = sb_dqopt(sb)->files[type]; + i_size = i_size_read(inode); if (off > i_size) return 0; @@ -5777,13 +5784,16 @@ static ssize_t ext4_quota_read(struct super_block *sb, int type, char *data, static ssize_t ext4_quota_write(struct super_block *sb, int type, const char *data, size_t len, loff_t off) { - struct inode *inode = sb_dqopt(sb)->files[type]; + struct inode *inode; ext4_lblk_t blk = off >> EXT4_BLOCK_SIZE_BITS(sb); int err, offset = off & (sb->s_blocksize - 1); int retries = 0; struct buffer_head *bh; handle_t *handle = journal_current_handle(); + type = array_index_nospec(type, MAXQUOTAS); + inode = sb_dqopt(sb)->files[type]; + if (EXT4_SB(sb)->s_journal && !handle) { ext4_msg(sb, KERN_WARNING, "Quota write (off=%llu, len=%llu)" " cancelled because transaction is not started", -- 2.17.1
