View Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0015954 | CentOS-7 | cryptsetup | public | 2019-03-25 22:46 | 2019-09-29 20:07 |
| Reporter | rfs | ||||
| Priority | normal | Severity | crash | Reproducibility | always |
| Status | new | Resolution | open | ||
| Platform | Intel SR1625URR | OS | CentOS | OS Version | 7.6.1810 |
| Product Version | |||||
| Target Version | Fixed in Version | ||||
| Summary | 0015954: When encrypted swap is enabled, using enough memory to activate swap crashes the entire system | ||||
| Description | All works well when swap not encrypted. When swap encrypted as below, running the program below (which just mallocs memory and writes to it all) causes a total system crash soon after it starts accessing swap space, with no disc activity going on, i.e. no swapping. No messages are left in /var/log/messages . Typically filesystems are left with multiple orphaned inodes. | ||||
| Steps To Reproduce | Put the following in /etc/crypttab (where <hostname> is replaced with the hostname or other name of a volume group): swap /dev/vg_<hostname>/lv_swap /dev/urandom plain,cipher=aes-xts-essiv:sha256,swap Put the following line in /etc/fstab, with no other swap space: /dev/mapper/swap none swap defaults 0 0 Reboot the system to effect those changes. Confirm that swap is configured as expected by swapon -s Filename Type Size Used Priority /dev/dm-2 partition 24707068 0 -2 # cryptsetup status swap /dev/mapper/swap is active and is in use. type: PLAIN cipher: aes-xts-essiv:sha256 keysize: 256 bits key location: dm-crypt device: /dev/mapper/vg_<hostname>-lv_swap sector size: 512 offset: 0 sectors size: 49414144 sectors mode: read/write Put the following program into domalloc.c in some directory: /* Program that does mallocs to order, freeing each one when the next one is requested. */ #include <stdio.h> #include <stdlib.h> int main(int argc, char **argv) { long int Nlongs = 0; long int *longs = NULL; long int nlong; printf("How many longs to malloc ?\n"); do { scanf("%ld", &Nlongs); free(longs); if ((longs = malloc(Nlongs * sizeof(long int))) == NULL) printf("malloc of %ld failed\n", Nlongs * 8); else { printf("malloc of %ld bytes succeeded\n", Nlongs * 8); printf("Writing (long int) ones into allocated memory\n"); for (nlong = 0; nlong < Nlongs; nlong++) longs[nlong] = 1; printf("Writing finished\n"); } printf("How many longs to malloc ?\n"); } while (Nlongs != 0); exit(0); } Compile it with gcc -o domalloc domalloc.c Run it with domalloc When it asks for a number of longs to allocate, enter a number slightly larger than the amount of memory you have divided by sizeof(long int). In another window run top and watch the memory in use creep up over the total physical RAM level; the system then crashes, without reporting completion of writing ones into the allocated memory. Rerunning the whole thing with an empty /etc/crypttab file and /etc/fstab containing /dev/mapper/vg_<hostname>-lv_swap none swap defaults 0 0 and rebooting then running domalloc in the same way leads to swap activity in the appropriate manner and successful conclusion with completion of writing message and a request to try a different amount to allocate. Note that to use swap at all, /proc/sys/vm/overcommit-memory should contain 0 If it contains 2, then one just gets malloc failed. | ||||
| Additional Information | Typical output of domalloc: $ domalloc How many longs to malloc ? 500 malloc of 4000 bytes succeeded Writing (long int) ones into allocated memory Writing finished How many longs to malloc ? 7000000000 malloc of 56000000000 bytes succeeded Writing (long int) ones into allocated memory <whole system crashes> | ||||
| Tags | No tags attached. | ||||
| abrt_hash | |||||
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Should have said that system has 48GiBytes of RAM, and if trying this out on a system with a different amount of RAM, then the number 7000000000 in the "typical output of domalloc" above should be set to something in between the total available size of RAM divided by 8 and the (total RAM plus total swap) divided by 8. |
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Same problem still present in CentOS 7.7 (1908). |
