6.16-stable review patch. If anyone has any objections, please let me know.
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From: Carlos Llamas cmllamas@google.com
commit 3ebcd3460cad351f198c39c6edb4af519a0ed934 upstream.
A process might fail to allocate a new bitmap when trying to expand its proc->dmap. In that case, dbitmap_grow() fails and frees the old bitmap via dbitmap_free(). However, the driver calls dbitmap_free() again when the same process terminates, leading to a double-free error:
================================================================== BUG: KASAN: double-free in binder_proc_dec_tmpref+0x2e0/0x55c Free of addr ffff00000b7c1420 by task kworker/9:1/209
CPU: 9 UID: 0 PID: 209 Comm: kworker/9:1 Not tainted 6.17.0-rc6-dirty #5 PREEMPT Hardware name: linux,dummy-virt (DT) Workqueue: events binder_deferred_func Call trace: kfree+0x164/0x31c binder_proc_dec_tmpref+0x2e0/0x55c binder_deferred_func+0xc24/0x1120 process_one_work+0x520/0xba4 [...]
Allocated by task 448: __kmalloc_noprof+0x178/0x3c0 bitmap_zalloc+0x24/0x30 binder_open+0x14c/0xc10 [...]
Freed by task 449: kfree+0x184/0x31c binder_inc_ref_for_node+0xb44/0xe44 binder_transaction+0x29b4/0x7fbc binder_thread_write+0x1708/0x442c binder_ioctl+0x1b50/0x2900 [...] ==================================================================
Fix this issue by marking proc->map NULL in dbitmap_free().
Cc: stable@vger.kernel.org Fixes: 15d9da3f818c ("binder: use bitmap for faster descriptor lookup") Signed-off-by: Carlos Llamas cmllamas@google.com Reviewed-by: Alice Ryhl aliceryhl@google.com Reviewed-by: Tiffany Yang ynaffit@google.com Link: https://lore.kernel.org/r/20250915221248.3470154-1-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/android/dbitmap.h | 1 + 1 file changed, 1 insertion(+)
--- a/drivers/android/dbitmap.h +++ b/drivers/android/dbitmap.h @@ -37,6 +37,7 @@ static inline void dbitmap_free(struct d { dmap->nbits = 0; kfree(dmap->map); + dmap->map = NULL; }
/* Returns the nbits that a dbitmap can shrink to, 0 if not possible. */