linux/samples/damon/prcl.c

174 lines
3.4 KiB

samples/damon/prcl: handle damon_start() failure damon_sample_prcl_start() callers assume it will clean up resources when it fails. And the function does the cleanup for context buildup failures. However, it is not doing the cleanup for damon_start() failure. As a result, when damon_start() fails, it leaks the memory for DAMON context. Free the context in case of the failure to fix the issues. Note that the issue can reliably be reproduced because the module calls damon_start() in the exclusive mode. For example, $ sudo damo start $ echo $$ | sudo tee /sys/module/damon_sample_prcl/parameters/target_pid $ echo Y | sudo tee /sys/module/damon_sample_prcl/parameters/enabled $ sudo cat /proc/allocinfo | grep damon_new_ctx Because the first command is running another DAMON instance, the third command fails the damon_start() call because the new DAMON instance cannot exclusively run. And without this fix, by repeating the third and the fourth commands above, we can show the memory consumption is only increasing due to the leaks. It requires the sudo permission though. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260628215447.96166-3-sj@kernel.org Link: https://lore.kernel.org/20260609145814.70163-1-sj@kernel.org [1] Fixes: 2aca254620a8 ("samples/damon: introduce a skeleton of a smaple DAMON module for proactive reclamation") Signed-off-by: SJ Park <sj@kernel.org> Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev> Cc: <stable@vger.kernel.org> # 6.14.x Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2026-06-28 14:54:41 -07:00
samples/damon/prcl: handle damon_start() failure damon_sample_prcl_start() callers assume it will clean up resources when it fails. And the function does the cleanup for context buildup failures. However, it is not doing the cleanup for damon_start() failure. As a result, when damon_start() fails, it leaks the memory for DAMON context. Free the context in case of the failure to fix the issues. Note that the issue can reliably be reproduced because the module calls damon_start() in the exclusive mode. For example, $ sudo damo start $ echo $$ | sudo tee /sys/module/damon_sample_prcl/parameters/target_pid $ echo Y | sudo tee /sys/module/damon_sample_prcl/parameters/enabled $ sudo cat /proc/allocinfo | grep damon_new_ctx Because the first command is running another DAMON instance, the third command fails the damon_start() call because the new DAMON instance cannot exclusively run. And without this fix, by repeating the third and the fourth commands above, we can show the memory consumption is only increasing due to the leaks. It requires the sudo permission though. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260628215447.96166-3-sj@kernel.org Link: https://lore.kernel.org/20260609145814.70163-1-sj@kernel.org [1] Fixes: 2aca254620a8 ("samples/damon: introduce a skeleton of a smaple DAMON module for proactive reclamation") Signed-off-by: SJ Park <sj@kernel.org> Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev> Cc: <stable@vger.kernel.org> # 6.14.x Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2026-06-28 14:54:41 -07:00
samples/damon/prcl: stop and free damon ctx when damon_call() fails damon_sample_prcl_start() calls damon_call() right after damon_start() is succeeded. The kdamond that has started by the damon_start() could be terminated by itself before or in the middle of the damon_call() execution. There could be multiple reasons for such a stop including monitoring target process termination and kdamond_fn() internal memory allocation failures. In the case, damon_call() will fail and return an error without cleaning up the DAMON context object. The damon_sample_prcl_start() caller assumes it would clean up the object, though. When the user requests to start DAMON again, damon_sample_prcl_start() is called again, allocates a new DAMON context object and overwrites the pointer for the previous object. As a result, the previous context object is leaked. Safely stop the kdamond and deallocate the context object when the failure is returned. Note that the kdamond should be stopped first, because damon_call() failure means not complete termination of the kdamond but only the fact that the termination process has started. The user impact shouldn't be that significant because the race is not easy to happen, and only up to one DAMON context object can be leaked per race. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260628215447.96166-7-sj@kernel.org Link: https://lore.kernel.org/20260610035214.4850-1-sj@kernel.org [1] Fixes: a6c33f1054e3 ("samples/damon/prcl: use damon_call() repeat mode instead of damon_callback") Signed-off-by: SJ Park <sj@kernel.org> Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev> Cc: <stable@vger.kernel.org> # 6.17.x Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2026-06-28 14:54:45 -07:00
samples/damon/prcl: stop and free damon ctx when damon_call() fails damon_sample_prcl_start() calls damon_call() right after damon_start() is succeeded. The kdamond that has started by the damon_start() could be terminated by itself before or in the middle of the damon_call() execution. There could be multiple reasons for such a stop including monitoring target process termination and kdamond_fn() internal memory allocation failures. In the case, damon_call() will fail and return an error without cleaning up the DAMON context object. The damon_sample_prcl_start() caller assumes it would clean up the object, though. When the user requests to start DAMON again, damon_sample_prcl_start() is called again, allocates a new DAMON context object and overwrites the pointer for the previous object. As a result, the previous context object is leaked. Safely stop the kdamond and deallocate the context object when the failure is returned. Note that the kdamond should be stopped first, because damon_call() failure means not complete termination of the kdamond but only the fact that the termination process has started. The user impact shouldn't be that significant because the race is not easy to happen, and only up to one DAMON context object can be leaked per race. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260628215447.96166-7-sj@kernel.org Link: https://lore.kernel.org/20260610035214.4850-1-sj@kernel.org [1] Fixes: a6c33f1054e3 ("samples/damon/prcl: use damon_call() repeat mode instead of damon_callback") Signed-off-by: SJ Park <sj@kernel.org> Reviewed-by: Zenghui Yu <zenghui.yu@linux.dev> Cc: <stable@vger.kernel.org> # 6.17.x Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2026-06-28 14:54:45 -07:00
samples/damon: fix damon sample prcl for start failure Patch series "mm/damon: fix divide by zero and its samples", v3. This series includes fixes against damon and its samples to make it safer when damon sample starting fails. It includes the following changes. - fix unexpected divide by zero crash for zero size regions - fix bugs for damon samples in case of start failures This patch (of 4): The damon_sample_prcl_start() can fail so we must reset the "enable" parameter to "false" again for proper rollback. In such cases, setting Y to "enable" then N triggers the following crash because damon sample start failed but the "enable" stays as Y. [ 2441.419649] damon_sample_prcl: start [ 2454.146817] damon_sample_prcl: stop [ 2454.146862] ------------[ cut here ]------------ [ 2454.146865] kernel BUG at mm/slub.c:546! [ 2454.148183] Oops: invalid opcode: 0000 [#1] SMP NOPTI ... [ 2454.167555] Call Trace: [ 2454.167822] <TASK> [ 2454.168061] damon_destroy_ctx+0x78/0x140 [ 2454.168454] damon_sample_prcl_enable_store+0x8d/0xd0 [ 2454.168932] param_attr_store+0xa1/0x120 [ 2454.169315] module_attr_store+0x20/0x50 [ 2454.169695] sysfs_kf_write+0x72/0x90 [ 2454.170065] kernfs_fop_write_iter+0x150/0x1e0 [ 2454.170491] vfs_write+0x315/0x440 [ 2454.170833] ksys_write+0x69/0xf0 [ 2454.171162] __x64_sys_write+0x19/0x30 [ 2454.171525] x64_sys_call+0x18b2/0x2700 [ 2454.171900] do_syscall_64+0x7f/0x680 [ 2454.172258] ? exit_to_user_mode_loop+0xf6/0x180 [ 2454.172694] ? clear_bhb_loop+0x30/0x80 [ 2454.173067] ? clear_bhb_loop+0x30/0x80 [ 2454.173439] entry_SYSCALL_64_after_hwframe+0x76/0x7e Link: https://lkml.kernel.org/r/20250702000205.1921-1-honggyu.kim@sk.com Link: https://lkml.kernel.org/r/20250702000205.1921-2-honggyu.kim@sk.com Fixes: 2aca254620a8 ("samples/damon: introduce a skeleton of a smaple DAMON module for proactive reclamation") Signed-off-by: Honggyu Kim <honggyu.kim@sk.com> Reviewed-by: SeongJae Park <sj@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2025-07-02 09:02:01 +09:00
samples/damon: fix damon sample prcl for start failure Patch series "mm/damon: fix divide by zero and its samples", v3. This series includes fixes against damon and its samples to make it safer when damon sample starting fails. It includes the following changes. - fix unexpected divide by zero crash for zero size regions - fix bugs for damon samples in case of start failures This patch (of 4): The damon_sample_prcl_start() can fail so we must reset the "enable" parameter to "false" again for proper rollback. In such cases, setting Y to "enable" then N triggers the following crash because damon sample start failed but the "enable" stays as Y. [ 2441.419649] damon_sample_prcl: start [ 2454.146817] damon_sample_prcl: stop [ 2454.146862] ------------[ cut here ]------------ [ 2454.146865] kernel BUG at mm/slub.c:546! [ 2454.148183] Oops: invalid opcode: 0000 [#1] SMP NOPTI ... [ 2454.167555] Call Trace: [ 2454.167822] <TASK> [ 2454.168061] damon_destroy_ctx+0x78/0x140 [ 2454.168454] damon_sample_prcl_enable_store+0x8d/0xd0 [ 2454.168932] param_attr_store+0xa1/0x120 [ 2454.169315] module_attr_store+0x20/0x50 [ 2454.169695] sysfs_kf_write+0x72/0x90 [ 2454.170065] kernfs_fop_write_iter+0x150/0x1e0 [ 2454.170491] vfs_write+0x315/0x440 [ 2454.170833] ksys_write+0x69/0xf0 [ 2454.171162] __x64_sys_write+0x19/0x30 [ 2454.171525] x64_sys_call+0x18b2/0x2700 [ 2454.171900] do_syscall_64+0x7f/0x680 [ 2454.172258] ? exit_to_user_mode_loop+0xf6/0x180 [ 2454.172694] ? clear_bhb_loop+0x30/0x80 [ 2454.173067] ? clear_bhb_loop+0x30/0x80 [ 2454.173439] entry_SYSCALL_64_after_hwframe+0x76/0x7e Link: https://lkml.kernel.org/r/20250702000205.1921-1-honggyu.kim@sk.com Link: https://lkml.kernel.org/r/20250702000205.1921-2-honggyu.kim@sk.com Fixes: 2aca254620a8 ("samples/damon: introduce a skeleton of a smaple DAMON module for proactive reclamation") Signed-off-by: Honggyu Kim <honggyu.kim@sk.com> Reviewed-by: SeongJae Park <sj@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2025-07-02 09:02:01 +09:00