The patch titled Subject: idr: fix idr_alloc() returning an ID out of range has been added to the -mm mm-hotfixes-unstable branch. Its filename is idr-fix-idr_alloc-returning-an-id-out-of-range.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------ From: "Matthew Wilcox (Oracle)" willy@infradead.org Subject: idr: fix idr_alloc() returning an ID out of range Date: Fri, 28 Nov 2025 16:18:32 +0000
If you use an IDR with a non-zero base, and specify a range that lies entirely below the base, 'max - base' becomes very large and idr_get_free() can return an ID that lies outside of the requested range.
Link: https://lkml.kernel.org/r/20251128161853.3200058-1-willy@infradead.org Fixes: 6ce711f27500 ("idr: Make 1-based IDRs more efficient") Signed-off-by: Matthew Wilcox (Oracle) willy@infradead.org Reported-by: Jan Sokolowski jan.sokolowski@intel.com Reported-by: Koen Koning koen.koning@intel.com Reported-by: Peter Senna Tschudin peter.senna@linux.intel.com Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/6449 Reviewed-by: Christian K��nig christian.koenig@amd.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
lib/idr.c | 2 ++ tools/testing/radix-tree/idr-test.c | 21 +++++++++++++++++++++ 2 files changed, 23 insertions(+)
--- a/lib/idr.c~idr-fix-idr_alloc-returning-an-id-out-of-range +++ a/lib/idr.c @@ -40,6 +40,8 @@ int idr_alloc_u32(struct idr *idr, void
if (WARN_ON_ONCE(!(idr->idr_rt.xa_flags & ROOT_IS_IDR))) idr->idr_rt.xa_flags |= IDR_RT_MARKER; + if (max < base) + return -ENOSPC;
id = (id < base) ? 0 : id - base; radix_tree_iter_init(&iter, id); --- a/tools/testing/radix-tree/idr-test.c~idr-fix-idr_alloc-returning-an-id-out-of-range +++ a/tools/testing/radix-tree/idr-test.c @@ -57,6 +57,26 @@ void idr_alloc_test(void) idr_destroy(&idr); }
+void idr_alloc2_test(void) +{ + int id; + struct idr idr = IDR_INIT_BASE(idr, 1); + + id = idr_alloc(&idr, idr_alloc2_test, 0, 1, GFP_KERNEL); + assert(id == -ENOSPC); + + id = idr_alloc(&idr, idr_alloc2_test, 1, 2, GFP_KERNEL); + assert(id == 1); + + id = idr_alloc(&idr, idr_alloc2_test, 0, 1, GFP_KERNEL); + assert(id == -ENOSPC); + + id = idr_alloc(&idr, idr_alloc2_test, 0, 2, GFP_KERNEL); + assert(id == -ENOSPC); + + idr_destroy(&idr); +} + void idr_replace_test(void) { DEFINE_IDR(idr); @@ -409,6 +429,7 @@ void idr_checks(void)
idr_replace_test(); idr_alloc_test(); + idr_alloc2_test(); idr_null_test(); idr_nowait_test(); idr_get_next_test(0); _
Patches currently in -mm which might be from willy@infradead.org are
idr-fix-idr_alloc-returning-an-id-out-of-range.patch mm-fix-vma_start_write_killable-signal-handling.patch