From 8c42dd78df148c90e48efff204cce38743906a79 Mon Sep 17 00:00:00 2001 From: Gerald Schaefer Date: Mon, 27 Feb 2023 20:03:00 +0100 Subject: [PATCH] s390/extmem: return correct segment type in __segment_load() Commit f05f62d04271f ("s390/vmem: get rid of memory segment list") reshuffled the call to vmem_add_mapping() in __segment_load(), which now overwrites rc after it was set to contain the segment type code. As result, __segment_load() will now always return 0 on success, which corresponds to the segment type code SEG_TYPE_SW, i.e. a writeable segment. This results in a kernel crash when loading a read-only segment as dcssblk block device, and trying to write to it. Instead of reshuffling code again, make sure to return the segment type on success, and also describe this rather delicate and unexpected logic in the function comment. Also initialize new segtype variable with invalid value, to prevent possible future confusion. Fixes: f05f62d04271 ("s390/vmem: get rid of memory segment list") Cc: # 5.9+ Signed-off-by: Gerald Schaefer Reviewed-by: Heiko Carstens Signed-off-by: Heiko Carstens --- arch/s390/mm/extmem.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/arch/s390/mm/extmem.c b/arch/s390/mm/extmem.c index 5060956b8e7d6..1bc42ce265990 100644 --- a/arch/s390/mm/extmem.c +++ b/arch/s390/mm/extmem.c @@ -289,15 +289,17 @@ segment_overlaps_others (struct dcss_segment *seg) /* * real segment loading function, called from segment_load + * Must return either an error code < 0, or the segment type code >= 0 */ static int __segment_load (char *name, int do_nonshared, unsigned long *addr, unsigned long *end) { unsigned long start_addr, end_addr, dummy; struct dcss_segment *seg; - int rc, diag_cc; + int rc, diag_cc, segtype; start_addr = end_addr = 0; + segtype = -1; seg = kmalloc(sizeof(*seg), GFP_KERNEL | GFP_DMA); if (seg == NULL) { rc = -ENOMEM; @@ -326,9 +328,9 @@ __segment_load (char *name, int do_nonshared, unsigned long *addr, unsigned long seg->res_name[8] = '\0'; strlcat(seg->res_name, " (DCSS)", sizeof(seg->res_name)); seg->res->name = seg->res_name; - rc = seg->vm_segtype; - if (rc == SEG_TYPE_SC || - ((rc == SEG_TYPE_SR || rc == SEG_TYPE_ER) && !do_nonshared)) + segtype = seg->vm_segtype; + if (segtype == SEG_TYPE_SC || + ((segtype == SEG_TYPE_SR || segtype == SEG_TYPE_ER) && !do_nonshared)) seg->res->flags |= IORESOURCE_READONLY; /* Check for overlapping resources before adding the mapping. */ @@ -386,7 +388,7 @@ __segment_load (char *name, int do_nonshared, unsigned long *addr, unsigned long out_free: kfree(seg); out: - return rc; + return rc < 0 ? rc : segtype; } /* -- 2.30.2