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SJ Park
e16b8d640e
commita16fd3ad9dupstream. Patch series "mm/damon: avoid division by zero from damos_quota_score()". DAMON_SAMPLE_MTIER and DAMON_LRU_SORT allow the user to trigger division by zero in damos_quota_score(). Avoid it by adding parameters validation checks. This patch (of 2): damos_quota_score() can trigger division by zero if the target_value is zero. DAMON_SAMPLE_MTIER lets users set the target_value via node0_mem_{used,free}_bp parameters. It doesn't guard zero value case, though. As a result, users can trigger division by zero. Fix the issue by returning an error when the user tries to start DAMON with zero node0_mem_{used,free}_bp parameter values. DAMON_SAMPLE_MTIER is just a sample module, but the consequence is quite bad. Also the zero node0_mem_free_bp parameter might look like a reasonable setup to some users. Hence, the issue might really happen in the real world. One reliable way to reproduce the issue is like below: # cd /sys/module/damon_sample_mtier/parameters # echo 4096 > node0_start_addr # echo 8192 > node0_end_addr # echo 8192 > node1_start_addr # echo 81920 > node1_end_addr # echo 0 > node0_mem_free_bp # echo Y > enabled # dmesg -w [...] [18792.235916] Oops: divide error: 0000 [#1] SMP NOPTI [...] [18792.242787] RIP: 0010:damos_quota_score+0x6f/0x480 [...] This issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260803134034.15217-1-sj@kernel.org Link: https://lore.kernel.org/20260803134034.15217-2-sj@kernel.org Link: https://lore.kernel.org/20260801202657.117135-1-sj@kernel.org [1] Fixes:c5e67d40a1("samples/damon/mtier: add parameters for node0 memory usage") Signed-off-by: SJ Park <sj@kernel.org> Cc: <stable@vger.kernel.org> # 6.17.x Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
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