From e873c74132f0c5f1452816cd9bb26208f0bba1e1 Mon Sep 17 00:00:00 2001 From: Shivank Garg Date: Sat, 22 Aug 2026 19:22:05 +0000 Subject: dmaengine: fix use-after-free in dma_chan_put() and dma_release_channel() When dma_device_put() drops the last reference on chan->device->ref, dma_device_release() runs and may free the dma_device along with its channels. dma_chan_put() then still reads chan->device->owner via dma_chan_to_owner() for the trailing module_put(). KASAN catches it: slab-use-after-free in dma_chan_put+0x3e6/0x4c0 Read of size 8 by task insmod/6319 Freed by task 6319: kfree+0x225/0x470 dma_chan_put+0x395/0x4c0 dmaengine_put+0xf8/0x160 Cache the module owner in dma_chan_put() before the put so the trailing module_put() does not need chan->device. Fixes: 8ad342a86359 ("dmaengine: Add reference counting to dma_device struct") Suggested-by: Sashiko Link: https://sashiko.dev/#/patchset/20260518-dmaengine-kref-fix-v1-1-4d6125048fb7@amd.com Reviewed-by: Frank Li Reviewed-by: Logan Gunthorpe Signed-off-by: Shivank Garg Link: https://patch.msgid.link/20260822-dmaengine-kref-fix-v5-3-d4a4ee47d927@amd.com Signed-off-by: Vinod Koul --- lib/kasprintf.c | 64 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 64 insertions(+) create mode 100644 lib/kasprintf.c (limited to 'lib/kasprintf.c') diff --git a/lib/kasprintf.c b/lib/kasprintf.c new file mode 100644 index 000000000..cd2f5974e --- /dev/null +++ b/lib/kasprintf.c @@ -0,0 +1,64 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * linux/lib/kasprintf.c + * + * Copyright (C) 1991, 1992 Linus Torvalds + */ + +#include +#include +#include +#include +#include + +/* Simplified asprintf. */ +char *kvasprintf(gfp_t gfp, const char *fmt, va_list ap) +{ + unsigned int first, second; + char *p; + va_list aq; + + va_copy(aq, ap); + first = vsnprintf(NULL, 0, fmt, aq); + va_end(aq); + + p = kmalloc_track_caller(first+1, gfp); + if (!p) + return NULL; + + second = vsnprintf(p, first+1, fmt, ap); + WARN(first != second, "different return values (%u and %u) from vsnprintf(\"%s\", ...)", + first, second, fmt); + + return p; +} +EXPORT_SYMBOL(kvasprintf); + +/* + * If fmt contains no % (or is exactly %s), use kstrdup_const. If fmt + * (or the sole vararg) points to rodata, we will then save a memory + * allocation and string copy. In any case, the return value should be + * freed using kfree_const(). + */ +const char *kvasprintf_const(gfp_t gfp, const char *fmt, va_list ap) +{ + if (!strchr(fmt, '%')) + return kstrdup_const(fmt, gfp); + if (!strcmp(fmt, "%s")) + return kstrdup_const(va_arg(ap, const char*), gfp); + return kvasprintf(gfp, fmt, ap); +} +EXPORT_SYMBOL(kvasprintf_const); + +char *kasprintf(gfp_t gfp, const char *fmt, ...) +{ + va_list ap; + char *p; + + va_start(ap, fmt); + p = kvasprintf(gfp, fmt, ap); + va_end(ap); + + return p; +} +EXPORT_SYMBOL(kasprintf); -- cgit v1.3.1