From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A6DE433F8B7; Sat, 21 Mar 2026 18:28:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774117699; cv=none; b=m3aPiUBtAHmK6GPiUzcZ0uaR9WmGd8+H2nSY4YaRC9D4wIA4HZeu2cFgdEY5LmQ3ofeT4dGx2YE6Rqzr5RFlc9bJyv9+guTYkylQ9aqTCRBY+O5I+WqpyDmkc2HUb5KtXunvOwyGmC+cKEYl5Ndan4eholKwzutQAzWWYGoUFk8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774117699; c=relaxed/simple; bh=5bvuYH2nYkmwa/qJhlFqbyqSeCvNyzrl03kVyQs7mRQ=; h=Date:To:From:Subject:Message-Id; b=PFAOQ0pNNLH7WtV8MW4oKz3GSeFiwlJ+69FsAIfsdi1ybQb+JoIwEQ4O86jxvxWypYXUngPw4JLYKje6VO+mdt6wlhQ08p5HmPEdkLxJyODIoHV4JoOLz4i/17bICm97X5UiYjimrRHS9dv8oFz86JI0UsrrdwC0vIiONTAZHV4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=mkbV8L62; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="mkbV8L62" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 69833C19421; Sat, 21 Mar 2026 18:28:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1774117699; bh=5bvuYH2nYkmwa/qJhlFqbyqSeCvNyzrl03kVyQs7mRQ=; h=Date:To:From:Subject:From; b=mkbV8L62LxkfxdW4nv+RzB0GYvwuMUxJKN1A2CDxQ4yPfFKVhfI8PVlsGrxObVOA2 f6/aK04b4E739QhsqTLtnjkFyscuSquE1RQ8jjNLcGsdTUduVUKSds4tBpvYNGy390 Y3UVyikQGo4iDShgGdgQ1AGepIklGJm5Q7OAOEtk= Date: Sat, 21 Mar 2026 11:28:18 -0700 To: mm-commits@vger.kernel.org,stable@vger.kernel.org,sj@kernel.org,objecting@objecting.org,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-damon-sysfs-check-contexts-nr-before-accessing-contexts_arr.patch added to mm-hotfixes-unstable branch Message-Id: <20260321182819.69833C19421@smtp.kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm/damon/sysfs: check contexts->nr before accessing contexts_arr[0] has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-damon-sysfs-check-contexts-nr-before-accessing-contexts_arr.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-sysfs-check-contexts-nr-before-accessing-contexts_arr.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via various branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there most days ------------------------------------------------------ From: Josh Law Subject: mm/damon/sysfs: check contexts->nr before accessing contexts_arr[0] Date: Sat, 21 Mar 2026 10:54:25 -0700 Multiple sysfs command paths dereference contexts_arr[0] without first verifying that kdamond->contexts->nr == 1. A user can set nr_contexts to 0 via sysfs while DAMON is running, causing NULL pointer dereferences. In more detail, the issue can be triggered by privileged users like below. First, start DAMON and make contexts directory empty (kdamond->contexts->nr == 0). # damo start # cd /sys/kernel/mm/damon/admin/kdamonds/0 # echo 0 > contexts/nr_contexts Then, each of below commands will cause the NULL pointer dereference. # echo update_schemes_stats > state # echo update_schemes_tried_regions > state # echo update_schemes_tried_bytes > state # echo update_schemes_effective_quotas > state # echo update_tuned_intervals > state Guard all commands (except OFF) at the entry point of damon_sysfs_handle_cmd(). Link: https://lkml.kernel.org/r/20260321175427.86000-3-sj@kernel.org Fixes: 0ac32b8affb5 ("mm/damon/sysfs: support DAMOS stats") Signed-off-by: Josh Law Reviewed-by: SeongJae Park Signed-off-by: SeongJae Park Cc: [5.18+] Signed-off-by: Andrew Morton --- mm/damon/sysfs.c | 3 +++ 1 file changed, 3 insertions(+) --- a/mm/damon/sysfs.c~mm-damon-sysfs-check-contexts-nr-before-accessing-contexts_arr +++ a/mm/damon/sysfs.c @@ -1749,6 +1749,9 @@ static int damon_sysfs_update_schemes_tr static int damon_sysfs_handle_cmd(enum damon_sysfs_cmd cmd, struct damon_sysfs_kdamond *kdamond) { + if (cmd != DAMON_SYSFS_CMD_OFF && kdamond->contexts->nr != 1) + return -EINVAL; + switch (cmd) { case DAMON_SYSFS_CMD_ON: return damon_sysfs_turn_damon_on(kdamond); _ Patches currently in -mm which might be from objecting@objecting.org are mm-damon-sysfs-fix-param_ctx-leak-on-damon_sysfs_new_test_ctx-failure.patch mm-damon-sysfs-check-contexts-nr-before-accessing-contexts_arr.patch mm-damon-sysfs-check-contexts-nr-in-repeat_call_fn.patch lib-maple_tree-fix-swapped-arguments-in-mas_safe_pivot-call.patch mm-damon-core-document-damos_commit_dests-failure-semantics.patch lib-glob-fix-grammar-and-replace-non-inclusive-terminology.patch lib-glob-add-explicit-include-for-exporth.patch lib-glob-replace-bitwise-or-with-logical-operation-on-boolean.patch lib-glob-clean-up-bool-abuse-in-pointer-arithmetic.patch lib-uuid-fix-typo-reversion-to-revision-in-comment.patch lib-inflate-fix-memory-leak-in-inflate_fixed-on-inflate_codes-failure.patch lib-inflate-fix-memory-leak-in-inflate_dynamic-on-inflate_codes-failure.patch lib-inflate-fix-grammar-in-comment-variable-to-variables.patch lib-inflate-fix-typo-this-results-to-the-results-in-comment.patch lib-bug-fix-inconsistent-capitalization-in-bug-message.patch lib-bug-remove-unnecessary-variable-initializations.patch lib-idr-fix-ida_find_first_range-missing-ids-across-chunk-boundaries.patch lib-decompress_bunzip2-fix-32-bit-shift-undefined-behavior.patch lib-ts_bm-fix-integer-overflow-in-pattern-length-calculation.patch lib-ts_kmp-fix-integer-overflow-in-pattern-length-calculation.patch lib-glob-initialize-back_str-to-silence-uninitialized-variable-warning.patch lib-bch-fix-signed-left-shift-undefined-behavior.patch lib-bch-fix-signed-shift-overflow-in-build_mod8_tables.patch