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commit777a8560fdupstream. Prevent a "BUG: unable to handle kernel NULL pointer dereference in filemap_read_folio". For the sleepable context, convert freader to use __kernel_read() instead of direct page cache access via read_cache_folio(). This simplifies the faultable code path by using the standard kernel file reading interface which handles all the complexity of reading file data. At the moment we are not changing the code for non-sleepable context which uses filemap_get_folio() and only succeeds if the target folios are already in memory and up-to-date. The reason is to keep the patch simple and easier to backport to stable kernels. Syzbot repro does not crash the kernel anymore and the selftests run successfully. In the follow up we will make __kernel_read() with IOCB_NOWAIT work for non-sleepable contexts. In addition, I would like to replace the secretmem check with a more generic approach and will add fstest for the buildid code. Link: https://lkml.kernel.org/r/20251222205859.3968077-1-shakeel.butt@linux.dev Fixes:ad41251c29("lib/buildid: implement sleepable build_id_parse() API") Reported-by: syzbot+09b7d050e4806540153d@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=09b7d050e4806540153d Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev> Reviewed-by: Christoph Hellwig <hch@lst.de> Tested-by: Jinchao Wang <wangjinchao600@gmail.com> Link: https://lkml.kernel.org/r/aUteBPWPYzVWIZFH@ndev Reviewed-by: Christian Brauner <brauner@kernel.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Andrii Nakryiko <andrii@kernel.org> Cc: Daniel Borkman <daniel@iogearbox.net> Cc: "Darrick J. Wong" <djwong@kernel.org> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>