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| author | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2025-03-14 16:09:57 -0300 |
|---|---|---|
| committer | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2025-03-21 15:46:48 -0300 |
| commit | ed6a68bac7cd056abda9008019c71b167f0362dc (patch) | |
| tree | 7ceb7f6403f423e4773724c518e537e13f140a3d /stdio-common/vfprintf-process-arg.c | |
| parent | 1894e219dc530d7074085e95ffe3c1e66cebc072 (diff) | |
| download | glibc-ed6a68bac7cd056abda9008019c71b167f0362dc.tar.xz glibc-ed6a68bac7cd056abda9008019c71b167f0362dc.zip | |
debug: Improve '%n' fortify detection (BZ 30932)
The 7bb8045ec0 path made the '%n' fortify check ignore EMFILE errors
while trying to open /proc/self/maps, and this added a security
issue where EMFILE can be attacker-controlled thus making it
ineffective for some cases.
The EMFILE failure is reinstated but with a different error
message. Also, to improve the false positive of the hardening for
the cases where no new files can be opened, the
_dl_readonly_area now uses _dl_find_object to check if the
memory area is within a writable ELF segment. The procfs method is
still used as fallback.
Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Arjun Shankar <arjun@redhat.com>
Diffstat (limited to 'stdio-common/vfprintf-process-arg.c')
| -rw-r--r-- | stdio-common/vfprintf-process-arg.c | 28 |
1 files changed, 18 insertions, 10 deletions
diff --git a/stdio-common/vfprintf-process-arg.c b/stdio-common/vfprintf-process-arg.c index 8d20493766..90b5e61ceb 100644 --- a/stdio-common/vfprintf-process-arg.c +++ b/stdio-common/vfprintf-process-arg.c @@ -324,16 +324,24 @@ LABEL (form_pointer): LABEL (form_number): if ((mode_flags & PRINTF_FORTIFY) != 0) { - if (! readonly_format) - { - extern int __readonly_area (const void *, size_t) - attribute_hidden; - readonly_format - = __readonly_area (format, ((STR_LEN (format) + 1) - * sizeof (CHAR_T))); - } - if (readonly_format < 0) - __libc_fatal ("*** %n in writable segment detected ***\n"); + if (readonly_format == readonly_noerror) + readonly_format = __readonly_area (format, ((STR_LEN (format) + 1) + * sizeof (CHAR_T))); + switch (readonly_format) + { + case readonly_area_writable: + __libc_fatal ("*** %n in writable segments detected ***\n"); + /* The format is not within ELF segments and opening /proc/self/maps + failed because there are too many files. */ + case readonly_procfs_open_fail: + __libc_fatal ("*** procfs could not open ***\n"); + /* The /proc/self/maps can not be opened either because it is not + available or the process does not have the right permission. Since + it should not be attacker-controlled we can avoid failure. */ + case readonly_procfs_inaccessible: + case readonly_noerror: + break; + } } /* Answer the count of characters written. */ void *ptrptr = process_arg_pointer (); |