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a=z/mQ4Ysz8XfWz/Q5cLBRGdckG28=:19 a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19 a=xqWC_Br6kY4A:10 a=vUbySO9Y5rIA:10 a=GoEa3M9JfhUA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VwQbUJbxAAAA:8 a=yPCof4ZbAAAA:8 a=lRyk7R2wpmETDg0olqEA:9 cc=ntf awl=host:12109 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMTE1MDE0MiBTYWx0ZWRfX1PTyppIG0/4l J8frmXGwuH9RN59dJwGzB5sPtxsi11KVJEGtyWtXWnVOhcal2hBH6bjcplF/pw/YnI32D4CEIGx 2eoLDKRqnSW2plUqu5CMRVp0gY5lEyi6YljS2JNeZECo+6OfJqRDAsQl3UneDr+/k2wrdQngZWq 4Ds20UuKkb+7RBsEsSw3bz2mS4XCIRi9rvEwFNyNh+4njJQ4DE7etf8fnJwDglMT5gJAtJ6lxaC MIYM9wIDzIOxns6Coa70CFIJnDgJygi1meVaISFUEBwiKfxKrY9sjh6qyv0Yb3ha4o8SA5Vp/oj JiWFdkkLM5YSICJXGtUAPmMDwqqfrr54OlENBoZ4NFWNnAleUNRl9C3P5W03n4uYnB6TAEAv+II gYpO4hC547lSW1oO2Ed//ML7xxkoTyCu8+gNFxmk0J0XFSqy2Egrkf2+ZMHQ7qiz5Gdipo/8AKc EyzE8uynW6iYz9oQXJmB4JwL9XBJiAzK48E1CLfo= X-Proofpoint-ORIG-GUID: Iv80dpVCXrdGF9Az7MHGkE6c6-oYDUk0 It is possible that the dup_mmap() call fails on allocating or setting up a vma after the maple tree of the oldmm is copied. Today, that failure point is marked by inserting an XA_ZERO entry over the failure point so that the exact location does not need to be communicated through to exit_mmap(). However, a race exists in the tear down process because the dup_mmap() drops the mmap lock before exit_mmap() can remove the partially set up vma tree. This means that other tasks may get to the mm tree and find the invalid vma pointer (since it's an XA_ZERO entry), even though the mm is marked as MMF_OOM_SKIP and MMF_UNSTABLE. To remove the race fully, the tree must be cleaned up before dropping the lock. This is accomplished by extracting the vma cleanup in exit_mmap() and changing the required functions to pass through the vma search limit. Any other tree modifications would require extra cycles which should be spent on freeing memory. This does run the risk of increasing the possibility of finding no vmas (which is already possible!) in code that isn't careful. The final four patches are to address the excessive argument lists being passed between the functions. Using the struct unmap_desc also allows some special-case code to be removed in favour of the struct setup differences. V1: https://lore.kernel.org/all/20250909190945.1030905-1-Liam.Howlett@oracle.com/ RFC: https://lore.kernel.org/linux-mm/20250815191031.3769540-1-Liam.Howlett@oracle.com/ Changes since v1: - All patches have been standardized to _start/_end with the prefix being vma and pg. - Thanks David (and Lorenzo) - Change WARN_ON_ONCE to VM_WARN_ON_ONCE - Thanks David - Drop static and let the compiler decide - Thanks Suren - Fix header/c variable name mismatch - Thanks Lorenzo & Pedro - Added to commit message about the vma search - Thanks Suren - Added to commit message about variable names - Thanks David - Fixed comment in free_pgtables() - Thanks Suren - Make free_pgtables() comment a kernel doc - Thanks Lorenzo - Fixed order of arguments to free_pgtables() - Thanks Suren - Added change log comment about cleaning up the failed dup_mmap() even when all vmas are copied. - Renamed UNMAP_REGION to UNMAP_STATE - Thanks Suren & Lorenzo - Split patch 8 into two. - Thanks Lorenzo Liam R. Howlett (10): mm/mmap: Move exit_mmap() trace point mm/mmap: Abstract vma clean up from exit_mmap() mm/vma: Add limits to unmap_region() for vmas mm/memory: Add tree limit to free_pgtables() mm/vma: Add page table limit to unmap_region() mm: Change dup_mmap() recovery mm: Introduce unmap_desc struct to reduce function arguments mm/vma: Use unmap_desc in exit_mmap() and vms_clear_ptes() mm/vma: Use unmap_region() in vms_clear_ptes() mm: Use unmap_desc struct for freeing page tables. include/linux/mm.h | 4 -- mm/internal.h | 8 ++- mm/memory.c | 71 +++++++++++++---------- mm/mmap.c | 97 ++++++++++++++++++++++---------- mm/vma.c | 54 ++++++++++-------- mm/vma.h | 47 +++++++++++++++- tools/testing/vma/vma_internal.h | 12 ++-- 7 files changed, 193 insertions(+), 100 deletions(-) -- 2.47.3