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    Subject[PATCH 4.9 63/63] fs/quota: Fix spectre gadget in do_quotactl
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Jeremy Cline <jcline@redhat.com>

    commit 7b6924d94a60c6b8c1279ca003e8744e6cd9e8b1 upstream.

    'type' is user-controlled, so sanitize it after the bounds check to
    avoid using it in speculative execution. This covers the following
    potential gadgets detected 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]
    * fs/f2fs/super.c:1552 f2fs_quota_read() warn: potential spectre issue
    'sb_dqopt(sb)->files' [r]
    * fs/f2fs/super.c:1608 f2fs_quota_write() warn: potential spectre issue
    'sb_dqopt(sb)->files' [r]
    * fs/quota/dquot.c:412 mark_info_dirty() warn: potential spectre issue
    'sb_dqopt(sb)->info' [w]
    * fs/quota/dquot.c:933 dqinit_needed() warn: potential spectre issue
    'dquots' [r]
    * fs/quota/dquot.c:2112 dquot_commit_info() warn: potential spectre
    issue 'dqopt->ops' [r]
    * fs/quota/dquot.c:2362 vfs_load_quota_inode() warn: potential spectre
    issue 'dqopt->files' [w] (local cap)
    * fs/quota/dquot.c:2369 vfs_load_quota_inode() warn: potential spectre
    issue 'dqopt->ops' [w] (local cap)
    * fs/quota/dquot.c:2370 vfs_load_quota_inode() warn: potential spectre
    issue 'dqopt->info' [w] (local cap)
    * fs/quota/quota.c:110 quota_getfmt() warn: potential spectre issue
    'sb_dqopt(sb)->info' [r]
    * fs/quota/quota_v2.c:84 v2_check_quota_file() warn: potential spectre
    issue 'quota_magics' [w]
    * fs/quota/quota_v2.c:85 v2_check_quota_file() warn: potential spectre
    issue 'quota_versions' [w]
    * fs/quota/quota_v2.c:96 v2_read_file_info() warn: potential spectre
    issue 'dqopt->info' [r]
    * fs/quota/quota_v2.c:172 v2_write_file_info() warn: potential spectre
    issue 'dqopt->info' [r]

    Additionally, a quick inspection indicates there are array accesses with
    'type' in quota_on() and quota_off() functions which are also addressed
    by this.

    Cc: Josh Poimboeuf <jpoimboe@redhat.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: Jeremy Cline <jcline@redhat.com>
    Signed-off-by: Jan Kara <jack@suse.cz>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/quota/quota.c | 2 ++
    1 file changed, 2 insertions(+)

    --- a/fs/quota/quota.c
    +++ b/fs/quota/quota.c
    @@ -17,6 +17,7 @@
    #include <linux/quotaops.h>
    #include <linux/types.h>
    #include <linux/writeback.h>
    +#include <linux/nospec.h>

    static int check_quotactl_permission(struct super_block *sb, int type, int cmd,
    qid_t id)
    @@ -706,6 +707,7 @@ static int do_quotactl(struct super_bloc

    if (type >= (XQM_COMMAND(cmd) ? XQM_MAXQUOTAS : MAXQUOTAS))
    return -EINVAL;
    + type = array_index_nospec(type, MAXQUOTAS);
    /*
    * Quota not supported on this fs? Check this before s_quota_types
    * since they needn't be set if quota is not supported at all.

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