From: Enlin Mu Date: Tue, 1 Aug 2023 06:04:32 +0000 (+0800) Subject: pstore/ram: Check start of empty przs during init X-Git-Tag: v6.1.61~1224 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=e95d7a8a6edd14f8fab44c777dd7281db91f6ae2;p=platform%2Fkernel%2Flinux-starfive.git pstore/ram: Check start of empty przs during init commit fe8c3623ab06603eb760444a032d426542212021 upstream. After commit 30696378f68a ("pstore/ram: Do not treat empty buffers as valid"), initialization would assume a prz was valid after seeing that the buffer_size is zero (regardless of the buffer start position). This unchecked start value means it could be outside the bounds of the buffer, leading to future access panics when written to: sysdump_panic_event+0x3b4/0x5b8 atomic_notifier_call_chain+0x54/0x90 panic+0x1c8/0x42c die+0x29c/0x2a8 die_kernel_fault+0x68/0x78 __do_kernel_fault+0x1c4/0x1e0 do_bad_area+0x40/0x100 do_translation_fault+0x68/0x80 do_mem_abort+0x68/0xf8 el1_da+0x1c/0xc0 __raw_writeb+0x38/0x174 __memcpy_toio+0x40/0xac persistent_ram_update+0x44/0x12c persistent_ram_write+0x1a8/0x1b8 ramoops_pstore_write+0x198/0x1e8 pstore_console_write+0x94/0xe0 ... To avoid this, also check if the prz start is 0 during the initialization phase. If not, the next prz sanity check case will discover it (start > size) and zap the buffer back to a sane state. Fixes: 30696378f68a ("pstore/ram: Do not treat empty buffers as valid") Cc: Yunlong Xing Cc: stable@vger.kernel.org Signed-off-by: Enlin Mu Link: https://lore.kernel.org/r/20230801060432.1307717-1-yunlong.xing@unisoc.com [kees: update commit log with backtrace and clarifications] Signed-off-by: Kees Cook Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c index 2384de1c2d18..1e755d093d92 100644 --- a/fs/pstore/ram_core.c +++ b/fs/pstore/ram_core.c @@ -518,7 +518,7 @@ static int persistent_ram_post_init(struct persistent_ram_zone *prz, u32 sig, sig ^= PERSISTENT_RAM_SIG; if (prz->buffer->sig == sig) { - if (buffer_size(prz) == 0) { + if (buffer_size(prz) == 0 && buffer_start(prz) == 0) { pr_debug("found existing empty buffer\n"); return 0; }