diff options
Diffstat (limited to 'gmon-Fix-allocated-buffer-overflow-bug-29444.patch')
| -rw-r--r-- | gmon-Fix-allocated-buffer-overflow-bug-29444.patch | 79 |
1 files changed, 79 insertions, 0 deletions
diff --git a/gmon-Fix-allocated-buffer-overflow-bug-29444.patch b/gmon-Fix-allocated-buffer-overflow-bug-29444.patch new file mode 100644 index 0000000..d4c6221 --- /dev/null +++ b/gmon-Fix-allocated-buffer-overflow-bug-29444.patch @@ -0,0 +1,79 @@ +From 801af9fafd4689337ebf27260aa115335a0cb2bc Mon Sep 17 00:00:00 2001 +From: =?UTF-8?q?=D0=9B=D0=B5=D0=BE=D0=BD=D0=B8=D0=B4=20=D0=AE=D1=80=D1=8C?= + =?UTF-8?q?=D0=B5=D0=B2=20=28Leonid=20Yuriev=29?= <leo@yuriev.ru> +Date: Sat, 4 Feb 2023 14:41:38 +0300 +Subject: [PATCH] gmon: Fix allocated buffer overflow (bug 29444) +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +The `__monstartup()` allocates a buffer used to store all the data +accumulated by the monitor. + +The size of this buffer depends on the size of the internal structures +used and the address range for which the monitor is activated, as well +as on the maximum density of call instructions and/or callable functions +that could be potentially on a segment of executable code. + +In particular a hash table of arcs is placed at the end of this buffer. +The size of this hash table is calculated in bytes as + p->fromssize = p->textsize / HASHFRACTION; + +but actually should be + p->fromssize = ROUNDUP(p->textsize / HASHFRACTION, sizeof(*p->froms)); + +This results in writing beyond the end of the allocated buffer when an +added arc corresponds to a call near from the end of the monitored +address range, since `_mcount()` check the incoming caller address for +monitored range but not the intermediate result hash-like index that +uses to write into the table. + +It should be noted that when the results are output to `gmon.out`, the +table is read to the last element calculated from the allocated size in +bytes, so the arcs stored outside the buffer boundary did not fall into +`gprof` for analysis. Thus this "feature" help me to found this bug +during working with https://sourceware.org/bugzilla/show_bug.cgi?id=29438 + +Just in case, I will explicitly note that the problem breaks the +`make test t=gmon/tst-gmon-dso` added for Bug 29438. +There, the arc of the `f3()` call disappears from the output, since in +the DSO case, the call to `f3` is located close to the end of the +monitored range. + +Signed-off-by: Леонид Юрьев (Leonid Yuriev) <leo@yuriev.ru> + +Another minor error seems a related typo in the calculation of +`kcountsize`, but since kcounts are smaller than froms, this is +actually to align the p->froms data. + +Co-authored-by: DJ Delorie <dj@redhat.com> +Reviewed-by: Carlos O'Donell <carlos@redhat.com> +--- + gmon/gmon.c | 4 +++- + 1 file changed, 3 insertions(+), 1 deletion(-) + +diff --git a/gmon/gmon.c b/gmon/gmon.c +index dee64803ad..bf76358d5b 100644 +--- a/gmon/gmon.c ++++ b/gmon/gmon.c +@@ -132,6 +132,8 @@ __monstartup (u_long lowpc, u_long highpc) + p->lowpc = ROUNDDOWN(lowpc, HISTFRACTION * sizeof(HISTCOUNTER)); + p->highpc = ROUNDUP(highpc, HISTFRACTION * sizeof(HISTCOUNTER)); + p->textsize = p->highpc - p->lowpc; ++ /* This looks like a typo, but it's here to align the p->froms ++ section. */ + p->kcountsize = ROUNDUP(p->textsize / HISTFRACTION, sizeof(*p->froms)); + p->hashfraction = HASHFRACTION; + p->log_hashfraction = -1; +@@ -142,7 +144,7 @@ __monstartup (u_long lowpc, u_long highpc) + instead of integer division. Precompute shift amount. */ + p->log_hashfraction = ffs(p->hashfraction * sizeof(*p->froms)) - 1; + } +- p->fromssize = p->textsize / HASHFRACTION; ++ p->fromssize = ROUNDUP(p->textsize / HASHFRACTION, sizeof(*p->froms)); + p->tolimit = p->textsize * ARCDENSITY / 100; + if (p->tolimit < MINARCS) + p->tolimit = MINARCS; +-- +2.33.0 + |