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| author | Avinesh Kumar <akumar@suse.de> | 2024-01-24 14:26:02 +0100 |
|---|---|---|
| committer | Petr Vorel <pvorel@suse.cz> | 2024-01-25 09:24:40 +0100 |
| commit | 6c4bf3a75f4ba17503bc2d8ba91a7514fdae995e (patch) | |
| tree | 4a13df04c13e9e81f059d4a751b7f4bef69d0fbd | |
| parent | 9062824a70b8da74aa5b1db08710d0018b48072e (diff) | |
| download | ltp-6c4bf3a75f4ba17503bc2d8ba91a7514fdae995e.tar.gz | |
mmap04.c: Avoid vma merging
We hit a scenario where new mapping was merged with existing mapping of
same permission and the return address from the mmap was hidden in the
merged mapping in /proc/self/maps, causing the test to fail.
To avoid this, we first create a 2-page mapping with the different
permissions, and then remap the 2nd page with the perms being tested.
Link: https://lore.kernel.org/ltp/20240124132603.16199-1-akumar@suse.de/
Reported-by: Martin Doucha <mdoucha@suse.cz>
Reviewed-by: Martin Doucha <mdoucha@suse.cz>
Reviewed-by: Petr Vorel <pvorel@suse.cz>
Signed-off-by: Avinesh Kumar <akumar@suse.de>
| -rw-r--r-- | testcases/kernel/syscalls/mmap/mmap04.c | 23 |
1 files changed, 16 insertions, 7 deletions
diff --git a/testcases/kernel/syscalls/mmap/mmap04.c b/testcases/kernel/syscalls/mmap/mmap04.c index f6f4f7c98..fa85deed1 100644 --- a/testcases/kernel/syscalls/mmap/mmap04.c +++ b/testcases/kernel/syscalls/mmap/mmap04.c @@ -17,8 +17,8 @@ #include "tst_test.h" #include <stdio.h> -#define MMAPSIZE 1024 -static char *addr; +static char *addr1; +static char *addr2; static struct tcase { int prot; @@ -44,14 +44,23 @@ static struct tcase { static void run(unsigned int i) { struct tcase *tc = &tcases[i]; - char addr_str[20]; char perms[8]; char fmt[1024]; + unsigned int pagesize; + int flag; - addr = SAFE_MMAP(NULL, MMAPSIZE, tc->prot, tc->flags, -1, 0); + pagesize = SAFE_SYSCONF(_SC_PAGESIZE); - sprintf(addr_str, "%" PRIxPTR, (uintptr_t)addr); - sprintf(fmt, "%s-%%*x %%s", addr_str); + /* To avoid new mapping getting merged with existing mappings, we first + * create a 2-page mapping with the different permissions, and then remap + * the 2nd page with the perms being tested. + */ + flag = (tc->flags & MAP_PRIVATE) ? MAP_SHARED : MAP_PRIVATE; + addr1 = SAFE_MMAP(NULL, pagesize * 2, PROT_NONE, MAP_ANONYMOUS | flag, -1, 0); + + addr2 = SAFE_MMAP(addr1 + pagesize, pagesize, tc->prot, tc->flags | MAP_FIXED, -1, 0); + + sprintf(fmt, "%" PRIxPTR "-%%*x %%s", (uintptr_t)addr2); SAFE_FILE_LINES_SCANF("/proc/self/maps", fmt, perms); if (!strcmp(perms, tc->exp_perms)) { @@ -61,7 +70,7 @@ static void run(unsigned int i) tc->exp_perms, perms); } - SAFE_MUNMAP(addr, MMAPSIZE); + SAFE_MUNMAP(addr1, pagesize * 2); } static struct tst_test test = { |