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nilfs2: fix null-ptr-deref in block_touch_buffer tracepoint
stable inclusion from stable-v5.10.231 commit b017697a517f8779ada4e8ce1c2c75dbf60a2636 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IB5KQZ Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b017697a517f8779ada4e8ce1c2c75dbf60a2636 -------------------------------- commit cd45e963e44b0f10d90b9e6c0e8b4f47f3c92471 upstream. Patch series "nilfs2: fix null-ptr-deref bugs on block tracepoints". This series fixes null pointer dereference bugs that occur when using nilfs2 and two block-related tracepoints. This patch (of 2): It has been reported that when using "block:block_touch_buffer" tracepoint, touch_buffer() called from __nilfs_get_folio_block() causes a NULL pointer dereference, or a general protection fault when KASAN is enabled. This happens because since the tracepoint was added in touch_buffer(), it references the dev_t member bh->b_bdev->bd_dev regardless of whether the buffer head has a pointer to a block_device structure. In the current implementation, the block_device structure is set after the function returns to the caller. Here, touch_buffer() is used to mark the folio/page that owns the buffer head as accessed, but the common search helper for folio/page used by the caller function was optimized to mark the folio/page as accessed when it was reimplemented a long time ago, eliminating the need to call touch_buffer() here in the first place. So this solves the issue by eliminating the touch_buffer() call itself. Link: https://lkml.kernel.org/r/20241106160811.3316-1-konishi.ryusuke@gmail.com Link: https://lkml.kernel.org/r/20241106160811.3316-2-konishi.ryusuke@gmail.com Fixes: 5305cb83 ("block: add block_{touch|dirty}_buffer tracepoint") Signed-off-by:Ryusuke Konishi <konishi.ryusuke@gmail.com> Reported-by: